The Difference Between Mass and Weight

There is a common perception that weight and mass are basically the same thing. This video aims to tease out the difference between mass and weight by asking people what makes a car difficult to push. The standard answer is that it is difficult to push because it's heavy. But heaviness is a measure of weight, the gravitational pull of the Earth attracting the car to Earth's center. When the car is pushed on a flat road, the force of gravity does not oppose the motion. Instead the resistance felt is an indication of the car's mass which determines its inertia. Inertia is the property of matter that means it tends to resist acceleration - the greater the mass, the less the acceleration for a given amount of force.

[@Ares4TW]

"Weight is mass in a gravity" Shortest definition I heard of it.

[@kadalimutyaveni6709]

W=mg thats it

[@ahmadejaz848]

*F=w=mg*

[@mephisto4618]

On earth , gravity is different on different bodies

[@ahmadejaz848]

@@mephisto4618 But if you know... that difference is negligible unless it's a really humongous mass

[@waldolemmer]

@@ahmadejaz848 No, it's not. g on earth = 9.8 g on mercury = 3.7 g on venus = 8.9 g on mars = 3.7

[@NeilCrabbe]

I remember the example I was given for this years ago. The idea is that an astronaut on the moon lifts up a big rock and because it weighs less than on earth he finds he can lift it with little trouble. So he decides to see how far he can kick it and breaks his toe because the inertia is the same as it would be on earth. Nice example, I thought.

[@shadowfire04]

lmao bro you're only 6 years late

[@cristian-bull]

:O

[@jakemartin9556]

@@shadowfire04 hahahahaha so are you

[@seekersaurabh]

@@shadowfire04 8 years🙃

[@crumbledpaperworks]

Simplification level of mass, weight and inertia concept, School < Veritasium < Neil's comment

[@pikdame]

Inertia totally is Dereks favourite word :)

[@mr.satrical3537]

+Pik Dame "Inertia is a property of matter"

[@bobthemity]

+FadedPenguins BILLBILLBILLBILLBILL

[@mudkip_btw]

INERTIA, IDIOTS!

[@pikdame]

I guess it is interesting though

[@kish5435]

Friction plays major role. With frictioless surface car can be move with slight force.

[@veritasium]

Yup, no one mentioned friction so I didn't deal with this, but I intended too. Think about pushing a car to get it going and then running in front and pushing it back to stop it. Now friction is helping you, but it's similarly difficult to accelerate as it is to decelerate. Cars really have very little rolling friction. Mu times the normal force doesn't really apply to something with wheels.

[@Mockingjay-es9xl]

Thanks

[@davidmudry5622]

Gravity does not PUSH or PULL down...A. Einstein

[@davidmudry5622]

Actually weight and the car being too heavy is right, but only when you try to push the car, because weight is a resistive reaction to being accelerated by a force that pushes or pulls no matter if the force is up, down, or laterally. On a Bus if you stand and hold onto something your WEIGHT will go backwards, forwards, and sideways at different times during the Bus ride.

[@luisc1402]

Without friction, it would also be hard to push. Because of it's mass it would be more pushing myself away using the car xD

[@r1rmyjj]

Inertia is why you do not want to get up in the morning in bed

[@renxula]

You're right on two levels. There's actually a thing called "sleep inertia".

[@octoii2418]

We overcome Newton's First Law of Motion every single day by getting out of bed😂😂

[@samkes1061]

Sleep inertia

[@worm3179]

nah that’s just the depression

[@valladcodm1322]

Our inertia is highest in the morning when we wake up xD

[@fanthomans2]

Inertia is really hard to get your head around and I love how you put a lot of effort to make people understand it. The problem is based on the wrong concepts in everyday life which children learn during their early years. And the education system in their later years can't really change their misconceptions correctly as we can see in your videos.

[@matthewferris248]

Did anyone notice the ghost car at 2:50??

[@jitheshmanakalath3350]

yeah..i did

[@agathangeloguimaraes8657]

Matthew Ferris It should be for video editing, look at the two people walking in the video background disappear and reappear forward.

[@danisaia]

This is caused by a video transition, "dissolve", often used when trying to disguise an editing cut.

[@ions2]

Quiet. I can't hear the eggs

[@STAG162]

Looks like he omitted about 2 seconds through editing, which would've been smooth had there not been 2 people walking by in the background, and the 'ghost car' trailed out of shot a bit quicker.

[@veritasium]

that's a good question. I have certainly been thinking about it recently... No plans just yet but perhaps

[@supptk]

Hey!

[@itslucaxbitch69]

There still seems to be some confusion.. Okay if you still don't get it : 1.) All matter has mass, mass is a fundamental property and it's measured in Kilograms (yea.. in pound too..). 2.) Weight is a force due to gravity, it is equivalent to your mass times the gravitational pull of the planet. You will weigh less on moon than you do on earth. 3) Inertia is more or less a concept, it does not a have a unit associated with it. Inertia is directly proportional to the mass. More the mass, more the inertia, more difficult the object is to move. 4) Weighing machines weigh your weight (Newtons) then convert it into KgF (dividing it with 9.8). It measures weight but shows something more closer to mass, so it's safe to put a kG behind it (yea.. or pounds..). 

[@brianluckenbill3606]

Agreed, except that pounds (lbs) are also a unit of force. The seldom mentioned unit for mass in the English system is slugs. 1lb = 1 slug * 1ft/s/s

[@itslucaxbitch69]

I like to stick with SI Units.

[@RastaPilot737]

Well lets say scales are calibrated to earths gravity

[@itslucaxbitch69]

Will Wong Because of the opposing force of friction. And I think your question can be answered by the fact that the force required to get an object moving from rest is more than force required to keep an object moving or accelerating. But still honestly I think I am misinterpreting your question.

[@linmp2709]

***** Well, how about this, a lighter object A is placed on a planet with greater g while heavier (greater mass) object B is on the Earth, both of them are initially relatively at rest. Here's a question: Which one（A or B） is harder to MOVE ? Is it really object B（greater inertia）？ →Maximum static friction←

[@Xidnaf]

I would have said that the difficulty in pushing the car is more due to friction, which is caused by the car's weight, then by the car's inertia.

[@aayushverma4878]

*mass. Weight would not act horizontally.

[@Xidnaf]

@@aayushverma4878 No, I was talking about weight, not mass. The weight acts vertically, which causes friction, which acts horizontally.

[@ars85202]

Xidnaf, i love your videos!

[@KTBWorld]

@@aayushverma4878 The frictional force acting on an object is proportional to the object's weight.

[@rehatas6059]

Actually no, friction isn't the main reason for car to lose its momentum. Its because the car has wheels so the friction convert linear momentum into angular momentum in this case. And angular momentum is what makes tires spin, do you think a non-spining wheel can move against friction ? Nope. Ok then what makes tires stop after a while? Its because of the imperfection of the tire. Tires don't contact with the ground on only one point. They stretch through the ground a bit so the ground applies reaction force on several points, which unsettles the torque and cause tire to lose its momentum. Basically why is it hard to move the car? Because its heavy :pp

[@MrValdasJ]

It`s amazing how you can make these videos that forces a viewer to think himself and keep guessing and come to right conclusion. bravo sir

[@dwightschrute3712]

I love how the guy at 2:37 just randomly threw in the word "momentum", to act like he knew what she was talking about.

[@robrobinhembram305]

Intelligent way to show off your expensive car.

[@drinkingthatkool-aid3193]

Lmao

[@jur4x]

+Robrobin Hembram Cheap old Peugeot? Not so sure.

[@auscaliber1]

Show off he doesn't know about cars more like. A convertible peugeot, for the man who likes jelly so much he wants to drive it as well as eat it.

[@Coreycry]

this Peugeot sure is more expensive than shoes, but I still wouldn't call it expensive car lol More importantly, I didn't know there were Peugeot in Murrica

[@samedman1]

Peugeot 306 roadster? Those go around for £800. No, not a show off.

[@tombombadil1351]

i would have questioned the friction on the wheels bearings tho. that was never mentioned. but with a bit more googling, it seems ball bearings are very effective at reducing friction

[@saurabhjarodia335]

But friction is dependent on gravity. Inertia on the other hand is fixed

[@tombombadil1351]

@@saurabhjarodia335 my point was if the wheel bearings did not reduce friction significantly(or at all), it would be practically the same as trying to push a giant concrete slab with the same mass as the car on a road. we can easily predict and assume correctly, a single person could not push such a slab with the friction force resisting their effort. inertia and friction both play a role in the resistance to changing the car's motion. and id be curious just to know what the proportion is of these when it comes to resisting

[@enriqueuret]

2:49 Ghost car!!!!!! :O

[@-_Nuke_-]

saw it too! lol wtf?

[@shahzadmughal7666]

Its because of camera's frame are missing

[@kidinmyheart8318]

Oh don't mind its harry potter's universe

[@radheymishra6089]

ghosts caught in camera

[@nripeshdhungana6342]

It's because of: 1. Inertia 2. Its mass 3. Its weight 4. Frictional force

[@DearHRS]

Mass (m) is the measure of inertia, weight (W) is the force attracting you towards the centre of the Earth (W=m*g) (g=gravitational acceleration, on average it's 9.8m/s^2) ,and friction is dependent on weight*coefficient of resistance between 2 materials, this formula is for sliding friction (not rolling which is in this case).... the actual answer why it is hard to push a car is, because of the mass, friction between wheels and tarmac, and resistance between gears (if car is not in neutral).

[@elephant_888]

You can eliminate mass (2) from the list since it's already accounted for in calculations for 1, 3, and 4.

[@mrnarason]

You neglected air resistance, marks off.

[@ayessarodado3955]

I was about say frictional force

[@pickle_256]

@@mrnarason in this situation air resistant is negligible

[@veritasium]

@HeyyLookItsAlex I got the car moving and then tried to stop it. Now friction is helping you but it's just as hard to stop it as it was to get it going. Plus we know that cars have very little rolling friction because they can go quite a ways just coasting.

[@vistakay]

Hello Veritasium from almost a decade ago

[@versatilegeniuses9374]

@@vistakay True fans we are

[@FirestormX9]

@@versatilegeniuses9374 The original comment was made at a time when having reply threads in comments was not even a thing!

[@versatilegeniuses9374]

@@FirestormX9 haha lol

[@louislopez55]

I don’t think cars go a ways because they have little rolling friction. They go a ways because they have mass. I have owned many motorcycles and they slow quickly when I close the throttle, in fact I can go down steep hills here in Arizona without even touching the brakes. (Even on a 600lb bike) In a car I always have to either brake, shift to a lower gear, or both. I would think the two relatively skinny tires on my motorcycle have less rolling friction than the four much larger tires on a car.

[@veritasium]

@edgarsucar I disagree. I was going to talk about this misconception too but not enough people mentioned it in interviews. Think about trying to stop a rolling car moving on a level surface. Now friction helps you but it's similarly difficult to stop as it is to get going. Inertia is the main effect, friction is secondary.

[@pablogomez8236]

@@Rustie_za I think 10 years ago you couldn't do that actually, so you can be infuriated with old KZbin platform 🤣

[@justalazyguy.0_0]

Damn this comment is beautiful

[@wlee55]

That is a great way to explain it! I'm using this video. Thank you, Derek.

[@awesomedaltonkids6212]

Weight is relative and mass isn't. Your weight on the moon is less than earth but your mass is the same. Its not semantics, they're different concepts.

[@willoughbykrenzteinburg]

I understand what you are trying to say, but _relative_ is certainly not the right word to describe it. Weight is a force. Mass is a fundamental property of matter. Weight depends on mass. Mass just is. Mass is indeed relative, but that has nothing to do with what this video is talking about, and it's not important.

[@sam5992]

@@willoughbykrenzteinburg relative to position

[@willoughbykrenzteinburg]

@@sam5992 that's not what relative means. Relative means that it depends on the OBSERVER'S position. Weight is absolute. All observers will measure the same weight of an object regardless of their position RELATIVE to that object. It is true that an object weighs less on the moon, but all observers regardless of their location will observe the same weight for that object on the moon, ergo it is absolute; not relative.

[@sam5992]

@@willoughbykrenzteinburg That's what they meant by the comment. Sorry you're offended. They meant that weight is dependent on the gravitational field it's in.

[@willoughbykrenzteinburg]

@@sam5992 I'm not offended. It's simply not what "relative" means. I said this in my original comment, and it still holds true. Imagine that... Imagine trying to correct a misconception, and upon correcting that misconception, you are rewarded with, "sorry you're offended". It would seem a bit silly, wouldn't it? You do you though... For example, you didn't actually make attempts to articulate a counter to my comment. You simply made an attempt to invalidate me as a source - and failed by the way. It's ok - I'm used to it. The sooner you put your pride aside and understand that I actually know what I'm talking about (because I'm thoroughly educated on the topic), the sooner you can correct your misconceptions. Isn't that great?! But no - you'd rather make petulant attempts at invalidating me because I dared to cross you. I'm still right. You could learn a lot from me, but your ego is too busy getting in the way. I get it. I even said as much in my original comment. Weight is indeed depdent on the gravitational field you are. However. THAT IS NOT WHAT RELATIVE MEANS....... In physics, "relative" has an explicit meaning - and this ain't it.

[@MoparMilan]

what to anwer whenever veritasium asks a question: INTERTIA

[@anitakocab8865]

*inertia

[@ferdaev7209]

What a mess sentence Don't reply to me

[@agerven]

True, but I hate that answer, or the word inertia. It is so abstract and confusing. You cannot do calculations on inertia. Instead you use conservational laws (conservation of energy and impulse). Basically inertia is a statement saying that whenever or however you want to change how an object moves, you need to exert a force on it. Object, move, force are all concepts that have a well defined and every day reality to them. Talking about inertia may be valid, but for me puts very real physics into an obscure magic theatre.

[@Bodyknock]

For people wondering about inertia, think of it this way. Force equals mass time acceleration. So if you apply a force to an object, by pushing it for instance, the amount it accelerates will be inversely proportional to its mass. The more massive the object, the slower it accelerates when you push it. Thus massive objects have a lot of inertia and take a lot of force to steer or push or pull.

[@tnorki]

I love how when he says something he makes a smile with open mouth like he just told a joke and is waiting for a laugh.

[@differencebetween6329]

That's surely a great explanation! Inertia is the key.. Good video. thumbs up.

[@taarap8191]

Did anyone see that car that popped out of nowhere at 2:50?

[@thienan5728]

damn

[@HijasFarook]

That's the Knight bus from the Wizarding world!

[@pronounjow]

I missed that the first time. Good catch! Maybe it's from a parallel universe? Lolbutsrsly

[@S0RpTV]

gosh u scared me the first time but when i checked it twice i realized that he added this thing to clarify what inertia/mass is

[@MrGreenAKAguci00]

Taarap From Gamers Pro // RobloxKid FGP ghosts are real.

[@veritasium]

@Ululuro Yes! as long as your car has good bearings, e.g. not a lot of rolling friction.

[@sirifail4499]

There’s also the rolling resistance of the tires and the friction in the wheel bearings and some drivetrain components resisting your push.

[@AtharvaVaidya]

I've been watching you since a while. Didn't realise how long until I realised I saw this video when it just came out and this was when I was already hooked to your channel. I hate that you and I grew up 😂 thank you for the years of beautiful science (emphasis on physics) content.

[@kazenna]

To be fair, static friction is directly proportional to an object’s weight, which is directly proportional to its mass, so it isn’t inherently wrong for them to say “it’s hard to push because it’s big” or “it’s heavy”

[@matszz]

Hmm, this is only half the tale, what about friction.

[@oldcowbb]

you have a wheel which you can pretty much ignore the friction

[@matszz]

oldcowbb No you can't ignore the friction. There's alot of friction going on both with the wheels and inside the car.

[@megascopstrichopsis798]

oldcowbb if there isn't friction the car would just slide across the road and the wheels wouldn't spin at all

[@oldcowbb]

i'm not saying there are no friction, but that is static friction which makes the wheel spin, and it does not affect the movement of the whole car, (assume wheels have negligible mass, assume it roll without slip)

[@matszz]

oldcowbb I work with trains, I can make a train car move about as easy as a car. That's because of the massive difference in friction. You can't ignore the friction. If the friction was negligble then the train car would be 50 times harder to push, I wouldn't be able to move it at all.

[@nikitampmaurya]

So glad I found your channel!

[@springboard9642]

First I love your demonstrations and explanations I will keep watching and I will show them to my children. There are to many variables involved in your car pushing example. The frictional forces involved in pushing your car were greater than those involved in changing it's momentum or the car would not stop once you got it moving. The best (and I think unrecognized) demonstration of inertia is the slow motion film of a water balloon being burst. The fact that the water hangs in the air, in balloon shape for even a second is the perfect example of inertia. Unfortunately it probably isn't the perfect demonstration. But the demonstrations are your specialty and I look forward to more.

[@willoughbykrenzteinburg]

Obviously, there is friction involved in this scenario. Imagine trying to stop a rolling car instead. In that scenario, friction is actually helping you, so the mass of the car would really be the only reason it would be hard to stop - that at least eliminates friction as much as possible as a culprit.

[@amazingmusti]

You are able to push the car because it has "wheels". take the same weight of the car, and make it into a box. you wont be able to push it, cause of the friction of the earth and resistance.

[@shreyabirje493]

On the contrary, it is the friction that causes the car (or us for that matter) to move in the first place..... You feel it is the 'wheel' because the rolling friction of the wheel is significantly less than the box 's static or kinetic friction.

[@amazingmusti]

+shreya birje No offense but I think you failed your science bad. Friction does not cause motion, friction is resistance. I wont even bother to comment on the second half of your comment, cause it is the most confusing comment I have heard so far. But wish you all the best if you are studying science.

[@shreyabirje493]

+Musti Sutarwala.. Well no offence to you too... My point was pretty easy to understand.... It was friction doesn't not always mean resistance to general motion.... It is resistance but to relative motion to itself .. Not just any motion... Also., The 'wheel' comment is just random in the video related to friction and inertia

[@amazingmusti]

+shreya birje General motion is the motion created by an outside force applied by another mechanical device. I dont know how, resistance to relative motion apply here, cause the object, which is the car is resting on a bearing like structure which has a rotational motion, and secondly the tire covers a very small area of connection to the ground, which compared to the mass of the object, the friction is minimum, cause motion is directly proportion to the mass of the object and the force applied, but inversely proportion to resistance.

[@RCSVirginia]

+Musti Sutarwala Science is not my field, but you put into words what I was thinking: "Try taking the tires off and let the car sit directly on the ground and see how easy it is to move." I knew that friction had to play some sort of a role.

[@ckarea55]

It is the friction man

[@saimanogyanat6037]

Thanks a lot veritasium!!! I've been learning a lot from your videos..

[@willoughbykrenzteinburg]

This is by F. Bell from "The Principals of Mechanics and Biomechanics" "In many real world situations the act of weighing may produce a result that differs from the actual weight. This is referred to as the apparent weight. A common example of this is the effect of buoyancy. When the gravitational definition of weight is used, the operational weight measured by an accelerating scale (such as in an elevator) is also referred to as the apparent weight."

[@dancoulson6579]

I always think of mass as it's resistance to change in motion. But weight is just how strongly it is attracted by gravity. So a car with a mass of 2000lb has a weight of 2000lb on earth. But in the middle of space, it only has a mass of 2000lb. But even though the car 'weighs' nothing in space, if you push away from it you will move much faster away from it, than the car will move away from you, relative to a stationary third party. If thing's lost their *mass* in space, you'd be able to flick the car away with a single finger at a very high speed.

[@veritasium]

no - friction is not the main effect - if you try to stop a rolling car, it is hard and in this case friction is helping you.

[@JKrollling]

I'm not quite sure about this inhertia talk, but just going through mechanics. the reason the car is hard to push compared to a basketball (this is sideways/perpendicular to its weight) is because it has a higher friction. friction is proportional to the reaction force, that's the stuff that stops the car going through the road

[@willoughbykrenzteinburg]

While friction plays a role, it is not the MAIN reason this car is hard to push. Friction is proportional to weight. So, suppose you had a scale model of this car that only had a mass of 10 kg. Now, suppose someone asked you why that scale model car was so easy to push compared to the larger car. What would your answer be? Would it be, "Because there is less friction in the scale model car"? Or would you say, "The scale model car is easier to push because it has less mass". If you want to blame friction for why the real car is hard to push, then you must also blame the lack of friction for why the scale model is easy to push because the friction:mass ratio is EXACTLY the same in both cases - however, you wouldn't say that the scale car was easy to push because it had less friction, would you? Of course not. Therefore, you can't BLAME friction for why it is harder to push - because the ratio is exactly the same. The reason this car is hard to push is because of its mass. If this car was in deep space, it would still be hard to accelerate at a reasonable rate. F = ma, so if you wanted to accelerate this car at 1 m/s² and its mass is 2,000 kg, then it will require a force of 2,000 Newtons to do so - - in deep space. This is 450 lbs. That's a LOT of force, and this doesn't even consider friction because you are in deep space. That's the point. And even if you want to blame friction, friction is a product of weight, and weight is a product of mass - - so still - - mass is the fundamental reason the car is hard to push.

[@JKrollling]

Willoughby Krenzteinburg no. friction is equal to the reaction force of an object multiplied by the coefficient of friction (confusing), if there was no friction, say the car was on the worlds best ice ring, any amount of force would push the car, granted it may only provide a small acceleration, but it will move nonetheless. The model car you speak of, it was again on this magic ice ring, no matter what its weight is, any force will make it move, it will just move faster as its mass is smaller. Don't try and correct someone unless you know you are right.

[@JKrollling]

Willoughby Krenzteinburg also you can't just assume that when you answer a question you just asked, and have little knowledge of mechanics, that i will agree with your answer

[@willoughbykrenzteinburg]

Daniel Brown​ I'm not wrong. This car is hard to accelerate _at a reasonable rate_ because of its mass. There is no debate about this. This car's static friction as it rests on the ground is somewhere in the neighborhood of 40 lbs. This is the force it will require to overcome static friction and get the car moving. That's not a lot of force compared to the mass of the car. Friction is very small in this case with respect to the mass of the car. In other words, the drag coefficient (which is not the least bit confusing, by the way) in this scenario is about 0.01. This coefficient represents the percentage of the normal force required to maintain a constant state of motion. With a drag coefficient of 0.01, it requires 1% of the normal force to maintain constant motion, or in other words, to continually counter friction equally. In this case, on level ground, it requires 1% of this car's weight to overcome friction. Any amount of force in excess of this 1% will accelerate the car. The average car's weight is about 4,000 lbs, so like I said, 40 lbs is the amount of friction here. Any adult human can exert a force of 40 lbs quite easily, so it would be careless, and just plain incorrect to make the claim that friction is the reason this car is hard to push. Friction is only accounting for 40 lbs of resistance. The entire mass of the car and its inertia is what is providing the rest of this resistance and making the car hard to accelerate _at a reasonable rate_. While you would get the car to move with any force in excess of a measly 40 lbs, the car will not lunge forward. It would barely roll, and even if you exerted 400 more pounds of force on this car, it would still only accelerate at about 1 m/s². Even though you are exerting a force that is TEN TIMES the resisting force of friction. Does this sound to you like this car is hard to push _BECAUSE OF FRICTION_??? If there were no friction, then it would STILL require 2,000 Newtons of force to accelerate a 2,000 kg car at just 1 m/s². Are you seriously rejecting this simple notion? And I will say this one more time incase it flew over your head. EVEN IF the force of friction were to blame for why this car was hard to push, that friction is a product of the normal force - - which in turn is a product of weight - - - which in turn is a product of mass. Mass is the fundamental property of this scenario which gives objects their weight - - which in turn provides the reactionary normal force. I am well aware of this; I just didn't think it necessary to go through every step. I assumed you were smart enough to be inherently aware of this concept. Apparently, that's one thing I was wrong about.

[@JKrollling]

Willoughby Krenzteinburg This is because you are thinking that the car has got its brakes on, which is another factor on top of friction. If you take a car, taking off the handbrake and holding the clutch down, you can push a car fairly easily, and im not saying at a ridiculous case of 1m/s/s, in that case after just 10seconds it would be moving over 20mph. Its basic mechanics that a particle (under basic mechanics conditions, which i'm sure you are acquainted with considering how high and mighty you think of yourself to criticise me) on a plane with zero friction, of any mass, will accelerate (not at your ridiculous 1m/s/s) no matter how small the mass is.

[@LECityLECLEC]

this is a creative and wonderful video thank you for doing this veri!!!

[@AxeAR]

So that's why I get in "I don't need sleep, I need answers" mode at 3am and don't wanna go to sleep, but then in the morning I don't wanna wake up?

[@CandidDate]

If you go to church, you have mass. If you're patient, you weight.

[@mahmudrahman9855]

thank you for clearing confusion

[@kumarnirup]

@veritasium Consider that there s no friction/gravity or any other force acting...n now how difficult or easy it would be to push cars with different masses?? Is inertia valid only under the influence of gravitational field?

[@HKAngne]

what about friction?

[@bhavukmathur2709]

I don't agree with the answer.. "Inertia" is just a term used to describe that without an external force, an object won't change its state of motion. But in our case, we are applying an external force to it.. What's happening here is that a reverse torque gets applied on the wheels by the ground (due to slight flattening of tyres) the very moment you try to push it. Also, there's friction between the internal parts of the car. These factors make pushing a car difficult. One can relate this to pushing a car with flattened tyres vs that full of air.. If you remove all this, anyone can push anything without any problem, the only difference being the "Acceleration" with which the object will move..

[@xXJeReMiAhXx99]

it would be almost as hard to get it going, there's hardly much friction at 0 kph, the majority by far has got to be just momentum.

[@huracan200173]

if you had a frictionless object, something like a car would still be difficult to accelerate. That's due to its mass, and therefore, it's inertia. You need a big force to accelerate such a massive object. I agree with you that you would be able to accelerate it so slightly, and since there's no friction, it would accelerate continuously (in a vacuum of course) so long as you're pushing it.

[@susanss70spartymix77]

Yep. F=ma Also, weight as it affects the friction via deformation of the tires.

[@SuperVstech]

Bhavuk Mathur I agree... Go to a lake, walk up to a large boat at a dock. The boat FAR outweighs the car... but you can push it easily... because water lifts it, canceling some weight, but the mass is still there... so INERTIA is all that’s keeping you from moving the boat, and a small bit of friction in the water.

[@DANGJOS]

@Amo Rise His point is that *any* force will cause a car to accelerate, if there's no frictional forces. A car is only hard to get moving because of the static friction in the internal parts, and between the wheel and ground, that makes it difficult to overcome.

[@srivastavamajjari]

Nice..Inertia is the property of matter that causes it to resist change in its state. It is basically the property that keeps things stand still or keeps moving.

[@rashmiranjannayak3251]

Well nice conversation but I; just to add another point to this; its not only weight but the frictional force between the wheel and rode and second is the state of inertia. Thanks for sharing.

[@fUtal1mistake]

Well, I guess in this case it's friction. Inertia still defines how hard it would be to make a car move with certain speed dp/dt = F (in vectors).

[@flagman57]

Ummm he's partially wrong when he's talking about inertia being the only thing responsible. The weight is partially responsible on a flat surface because the F (friction) = u(coefficient of friction) * F(Normal) and on a flat surface F(Normal) = - Weight. There is a bit of friction involved. So... that's mostly why a heavy rock would be hard to move, not the inertia.

[@HaroWorld1]

inertia is mostly why a heavy rock is hard to move friction is NOT THE MAIN REASON why a heavy rock is hard to move.

[@flagman57]

HaroWorld1 I don't think you read what I said... It takes negligible force to move a rock in space. Knowing that, reread what I posted. If you need clarification, just reply again.

[@ScienceNerd3336]

@@HaroWorld1 Friction absolutely does play a role. Let's think about this for a moment. Say the coefficient of static friction between the tires and the dry road is about 0.62 and the mass of the car is 1500 kg. To be able to figure out the maximum static friction, we must perform Newton's second law of motion: 1. In the y-direction, there's force normal and force of gravity, so it's F(Normal) - F(Gravity) = (mass of car)(acceleration in y-direction). Because the car isn't moving in the y-direction, we say that it's F(Normal) - F(Gravity) = 0 ===> F(Normal) = (Mass of Car)(9.81 m/s^2). 2. Now that we have the formula for Force Normal, we can plug this into the Force of Static Friction Equation to figure out the maximum force of static friction, which is F(static friction maximum) = (Coefficient of Static Friction) (Force Normal) = (0.62)(1500 kg)(9.81 m/s^2) = 9123.3 N. 3. That Maximum Force of Static Friction indicates that if you exceed a force applied on the car of 9123.3 N, the car will then begin to move, thus turning the Force of Static Friction into Force of Kinetic Friction.

[@DyingFlamex]

@1veritasium Is it the reason why the car is hard to push, because of friction. So the weight of must play role in the friction, as Normal reaction = Weight of car (assuming there is no upthrust under the car due to wind) and the fact that Friction = μR means the reason why the car is hard to push (partly) because of it weight? Thanks for reading!

[@soloplayer9015]

Really nice explanation...

[@veritasium]

disagree. You want as much friction between the tires and the road as possible. The friction that impedes your motion is rolling friction in the bearings that hold the axles. This is minimal, which explains why it is tough to bring a rolling car to a stop - inertia! This is difficult even though friction is helping you.

[@leonardomendoza5902]

There's a Ghost car @ 2:51 anyone? No?.. Thumbs Up!👍

[@MakiD2010]

LOOL I thought I was the only one who saw it.

[@saadansari2241]

There is a wormhole

[@ren3533]

Back to the future perhaps lol

[@swatigetsmail]

Nice video...very informative

[@aryaanjetha6061]

your videos really help

[@veritasium]

yeah for me mass and inertia are basically the same - and they are different from weight (which is gravitational force). So I have no problem with you saying cars are hard to push because they have a lot of mass.

[@gautampanchal457]

Can mass be termed as measure of inertia or vice - versa...?

[@janboleila]

​@@gautampanchal457it is

[@AlchemistOfNirnroot]

Well, you could argue it's difficult to push due to its weight using a free body diagram. By modelling the car as a particle (so all forces act at its centre) it has weight downward which is equal to the reaction force between the surface and car. Considering that friction is proportional to the reaction force, you can say that friction is proportional to its weight - which is equally correct. So it's difficult to push since its weight is responsible for the friction between the road and the tyres. However, you could quite easily say the same for mass since the coefficient of friction and gravitational field strength are just constants, therefore the frictional force is proportional to mass by this combined constant. My point is that to answer this question (why is the car difficult to push?) mass and weight are responsible but it's gravity which is truly responsible and the fact that surfaces IRL create resistive forces.

[@blakesnipe5347]

The car would be hard to push in the absence of gravity as well. This is the point. If the car were floating freely in deep space with a mass of 2,000 kg, and you wanted to accelerate it at just 1 m/s², it would require a force of 2,000 Newtons (450 pounds) to do so. It is also hard to STOP a moving car despite the fact that gravity is HELPING you in that case.

[@balaaps]

Nice video. You should also do a video on the difference between current and electricity

[@M_K-Bomb]

Smart! This is an amazingly good example

[@Kaervek87]

"Surprise! It's inertia!" *doesn't explain what inertia is*

[@MrLethalShots]

Jon R I hate when people just answer questions with “inertia!”. It’s so vague. Just speak in terms of mass. I’m 3 years into a physics degree and I’ve never once heard a lecturer use the word inertia in a context like this.

[@honkycrackergang9123]

@@MrLethalShots offofooopopphoiphzohihohohzgzhooohozhiooohoiooxzooohioozhooooooohzhzoiozhohzhoozhooohzzooohozhoxoocxhzipphipizho🤣😇🦝😍😇😍🤣😇🤣🤣😇🤣😄🤣🤣😇😄😍🤣😇😇😇😄😇😍😇😄🦝😍😇🤣😍🤣😇😄😇🦝😇😄😇🤣😄😡🤣🥰😆😞😆😞🥰🤨😉😝😝😡🧐😡😝😡😢😢😝😡😝😡🧐😡😡😡😝😢😝😔😡😢😗😣😝😣😱🤥🤬😫😲😫🤗😶😵😝😣🤥😱🤥🤗🤗😕🤗😕🤥😕🤬🤥🤥😟😱😟😱😕😢😕😖😕😕😕😕😕😢🤥😕😓😢😱😱😏😓😏😢😓😓😱😢😱😏😱😢🥳😓😱😣😱😢😏😓😏🤗🤬🤫😢😱🤬😫😫😲😶🤔😯😸😔😝😄😋😄🤣🙂🤣🥰🙂🙂🙂🙂😄🙂😄😋😋🥸🙂😁🙂🙂🙂😉☹️☺️☹️☹️🤨🤩☹️😗😫😶😱😱🤗😝😇😄😄😇😇😇😇😄😄😇😄😝😇🤨😇😝😝😇😄😄🤨😇😍🥸😱😫😱😫😱😶🤬😤😶😤😤😏😓😏😓😱😢😓😓😓😓🤬😕🧑🏾‍🍳🧑🏾‍🍳🧑🏾‍🚒👩‍🚀🧟‍♂️🙇‍♂️🧛🏽‍♀️🧛🏽‍♀️🧟‍♂️🤦🏾‍♀️🤦🏾‍♀️🇱🇺🇱🇧🇲🇾🇱🇧🇲🇾🇯🇴🇯🇲🇱🇧🇱🇧🇲🇭🇯🇲🇲🇾🇱🇧🇯🇲🇯🇴🇱🇧🇯🇲🇯🇴🇲🇼🇱🇹🇯🇲🇰🇿🇱🇹🇲🇽🇳🇦🇱🇷🇲🇻🇳🇮🇳🇵🇵🇱🇵🇪🇷🇺🇲🇵🇸🇸🇸🇬🇷🇼🇸🇧🇸🇪🇻🇨🇹🇨🇹🇭🇹🇨🇹🇱🇸🇾🇸🇾🇹🇨🇸🇾🇻🇦🇻🇦🇺🇸🇹🇨🇺🇸🇻🇦🇹🇨🇻🇦🇸🇾🇻🇦🇺🇸🇻🇦🇹🇴🇸🇾🇺🇸🇹🇨🇸🇾🇹🇹🇸🇾🇹🇨🇿🇦🇱🇹🙂🤪🇻🇨😄😄🇸🇸😍🇸🇸😍🇸🇸🇸🇸😄😄🤪🙂😆🤣😁👷🕵🏽‍♀️🕵🏾‍♀️🕵🏽‍♀️😉☹️☹️😉🙃☹️😔😉😉☹️😉☹️😉😉🥰😉☹️🇹🇭😍🇹🇴🇻🇨🇻🇨😍🤣🤣🇻🇨😄🇹🇴😍😍😄😄🤣😄🤣😍😍😍🤣😄🇹🇭🇻🇨🇹🇭🇻🇨😄🇻🇨🇹🇭🇹🇭😍😄🇻🇨🤣😍😍😄🇹🇴😍😄🤪🇹🇭🇹🇭🇹🇱🇹🇱🇻🇦🤪😇🇹🇭🇹🇭🤪🤪😆🤪😇🇹🇭🤪👨🏾‍🏫👨🏾‍🏫👩🏾‍💻🧟‍♀️🧙🏾🧙🏾🧙🏾🧞‍♂️🧟‍♂️💾🧭💾🧭💻💾💾🧭🕹📞💾💾🧭💾🖱⌛️⌨️🧭📸☹️🧟‍♂️☹️😇💻😇😇☹️💻☹️💻😂⌨️⌨️☹️😂💻🧟‍♂️😄💻⌨️💻☹️💻☹️🥱😑😷🙀👿🙀💩👾🤖👾👊🤯♎️☯️💗💟☯️💟♎️💗💗💟♒️☯️💗☯️👨‍👨‍👦👨‍👧‍👧👨‍👨‍👦👩‍❤️‍💋‍👨👨‍👦👩‍❤️‍💋‍👨👨‍👧‍👧👩‍❤️‍💋‍👨👩‍❤️‍💋‍👨👩‍👩‍👦👨‍👧‍👧👨‍👨‍👦👨‍👨‍👦👨‍👧‍👧👩‍❤️‍💋‍👨👨‍👩‍👧👨‍👨‍👦👨‍👧‍👧👩‍👩‍👦👨‍👨‍👦👩‍❤️‍💋‍👨👨‍👨‍👦👨‍👧‍👧👨‍👦🧥👩‍👦👩‍👩‍👧👩‍❤️‍💋‍👨😄😄😄😇👿😄😍😄⌨️👊😚💗🤖☯️🤖💗💟🤖♒️💗😄😇😄🤖💟🤖💗💟🤣🙂😚😚🙀😄🙀🤨😉🤩😢😣😣😔😉☹️😉😘🤨😔😉🧐😣🤥🤨😉😔😉☹️😔😋😉😔🤨😉☹️😉👷🏾🤨☹️🤨🤨😉☹️😉🤨😔🤨😋☹️😉👷🏾👷🏾👷🏾👷🏾🧑‍💻😋😉🤨🙃😔😔😉🤨😉😘😙😄😄🙂😄🙂🙂🙂👨‍👧‍👧😇😇🙂😆🤣🥰☯️☺️🥰🤩😘😄😷😐🤭😐🥱🤠🥱🥱💗🕉♒️💗🕉☯️☯️💗💟💗💟☯️♎️♎️☯️💗♎️💟💗♎️💗💗☦️🈚️☮️♓️♎️💮🆎🈵🈸⭕️⭕️🈸⚛️🆎🚳🛑😄🙂🙂😚😄🤨🤨😄😄😚😣🤨😄🙂😣🙂😣🙂😣😣🤨🤨😄🙂😚😄😚😄😚🤨😚😇🤨😄😇🤭🤐😐😐🥱😐🥱🥱🦠🚽🧸🦠🧼🧸🧸🧹🦠🪑🧼🦠🦠🧼🦠🪑🦠🧸🚽🧼🦠🧼🦠🪑🧼🧼🦠🪑⛔️♻️♻️㊙️❗️⭕️🈲🈲❗️❗️💯‼️💯💯🈲‼️⭕️‼️💯❗️🆑💯‼️🈲‼️❗️🈲⭕️❗️🆑💯💯🆑🈲💯🈲❗️💯‼️‼️🈲♻️💢🅾️🅾️♻️⛔️🚸⁉️🔞❎🔆💤❎🔆🧨🧨😚😄🙂🪑🅿️❓✅✅❓💤🅿️❓🚸🅿️✅🔅❓✅❓🅿️🅿️✅❓👷🏾👨🏽‍🌾👨🏽‍🌾😯😲😤😲😭😲😤😄🕵🏽‍♀️🕵🏽‍♀️👨🏽‍🌾👨🏽‍🌾

[@asded6844]

This makes me miss physics class. i use to be able to answer some of this.

[@carlbrown2805]

Same here , I learned this and it was in my head but I just couldn't remember

[@oomrp]

thank you for this video, I just showed it to a student; saving me the frustration of explaining it to that student for the 10 th time this year. why is this such a hard concept?

[@heart0fthedrag0n]

The car is difficult to push also because of friction. Things with wheels have relatively low friction, compared to things that don't (that's why you can push a 1 ton car, but not a 1 ton rock) but the rubber tires still have quite a lot of friction with the ground, compared to something like, for example, a train track. This is why you can just as easily push a train wagon that weights 30 times more than the car. I live next to a train depot and as kids we had lots of fun pushing old train wagons around :D

[@TheJmiller1993]

Are you a physicist or an inertiaist

[@fotismixalopoulos6911]

can enyone see the car on the left 2:50 like gost lol

[@AA-100]

Video editing

[@willoughbykrenzteinburg]

What is the source of the static friction? I can see rolling resistance playing a part, but not static friction.

[@xoppa09]

there is also static (and kinetic) friction, in addition to inertia, that makes it difficult to push. if you want to measure pure inertia, you would need a frictionless surface such as ice, or a car floating suspended on air

[@claycoppinger2983]

The videos in which you play Socrates and ask people question after question are painful to watch. You are pandering to low in my opinion.

[@moshikon44]

you could also say that he makes people think about things they do not usually think about.

[@purrability]

Hey Derek, I have a question. I know it has nothing to do with the mass or weight... Or maybe it does without me knowing about it. The question: How can there be natural fission reactors? Or better said: How do they work? Thanks!

[@duckduckgo358]

So theoretically if it was on like a magnetic track levitating would it still be slower to push then a less massive object

[@sarthakverma13]

People 13 years ago were smart, now if you'll ask the same question it would be hard to find even a single person giving correct answer.

[@PranRaj94]

i would say to overcome the inertia of rest easily. there is less friction on offer due to the free spinning wheels if the car is in neutral. there is also no resistance from engine or transmission resisting that force being applied on the car when we push it.. weight doesn't really matter that much as long as the resistance within the drivetrain and bearings are low

[@APEX_GAMING922]

Congratulation for 15 million love from bangladesh 🇧🇩

[@s.xurxbh]

From his oldest video and till now this video i have answered all the questions correctly.....being and IIT JEE aspirant From INdIA it was quiet easy

[@nanu1980]

2:18: The answer is also: friction. Especially where two surfaces are forced together by gravity. Of course in this case, friction has deliberately been reduced by various mechanism, because we want cars (=heavy objects) to actually move. So we put weels under them, grease the axes and everything that's supposed to be moving to reduce friction. If an object with the size and the mass of tat car was sitting on the street without weels or ice or grease or anything that would reduce friction, we couldn't push it, I think. And that would be directly linked to gravity. Because gravity would be responsible for a great part of the amount of friction.

[@willoughbykrenzteinburg]

You are exactly right. Friction certainly is a function of weight. HOWEVER, weight is a function of mass, so without that mass, you don't get the friction, so ultimately, even if friction were the MAIN reason it was hard to push, mass is still the fundamental reason. In other words, if you had an exactly proportional scale model of this car that had a mass of just 1 kg, and you asked people why it was EASY to push, I doubt you would find a single person that would claim that it was easy to push because of the LACK of friction on the car. As I assume you understand, that friction is DIRECTLY proportional to the mass/weight of the car, so the amount of friction in THIS scenario bears the exact same friction : weight ratio. If you do not assert that the scale car was easy to push because of the LACK of friction, then you shouldn't BLAME friction for why the actual car is harder to push. I think the point he was trying to make is that a lot of people probably don't understand that this car would still be hard to accelerate even if it were in deep space far away from any gravitational influence. I think a lot of people think that if the car were weightless, then you could move it around as if it were a feather, and that is certainly far from the case. The rest of this comment is just going to do the math for your scenario where the car is subject to static friction vs rolling resistance (which is the friction present here). Static friction would be the main reason the car would be very hard to push if you took away the tires like you were talking about. You don't have to actually take off the tires. Let's just assume they don't roll, because the fact that the tires 'more or less' freely roll is what makes this car relatively easy to push. The equation to calculate friction is really very simple. It's just the Normal force times the friction coefficient. In our scenario, the Normal force is equal to the weight since we are talking about level ground. The coefficient of friction for rubber on concrete is 1 (I got this figure from simply looking it up on a table). A coefficient of 1 is easy to work with. It just means that the force of friction is equal to the Normal force. If the car's mass is 2,000 kg, then it's weight is 19,600 Newtons. The force of friction is ALSO 19,600 Newtons with this coefficient. That's about 4,400 lbs. This means that you would have to push the car with over 4,400 lbs of force before it would overcome friction and move, so yeah. You are right. If you removed the rolling mechanism from the car (locked the brakes), no human could possibly push it, and friction would certainly be the reason. But, like I said before, ultimately, friction is still a function of mass fundamentally, so mass is still the fundamental reason. WITH the wheels able to turn freely, static friction is no longer applicable (in the traditional sense). Now, we are only dealing with rolling resistance (ignoring negligably tiny sources from the greased inner workings of the car, axle, driveshaft, etc.). The coefficient of rolling resistance for that same rubber on concrete is .01. This means that the force of friction is about 1% of the weight in this same scenario, so this same car requires only 44 lbs of force to overcome the friction with rolling tires. And a human CAN push this car. In the grand scheme of things, I think 44 lbs of friction is pretty small when compared to the weight of the car, so its inertia is still the main reason it is hard to push.

[@nanu1980]

Willoughby Krenzteinburg You said:"so ultimately, even if friction were the MAIN reason it was hard to push, mass is still the fundamental reason." First of all, there is no contradiction to what i said. Because mass and gravity in interaction (which means "weight") is what increases or even produces the friction in this scenario. I was not aguing against MASS as critical element here. I was aguing against how he constructed the argument in the video, t maje himself look smart and the other people look unknowledgeable. ^^ At 2:05 he asks the woman why the car is hard to push. At 2:18 he answers it with "inertia" only, not mentioning the role of friction at all. He wants to make it seem like most people's answers to this question (because it is heavy) is wrong. When in fact it isn't wrong. It is partially correct. It's just not the whole story and their internal model of the situation may not be very elaborate. But it works for everyday lif and conditions that we find on earth. For most situations on earth, mass automatically means, that there is weight, because we do have gravity. Like you said, friction is, like inertia, a function of mass. So, you and i are actually in accordance. It's just that he wanted to interpret peoples answer "It's hard to push, because it's heavy" as "It's hard because gravity". It's hard because it's heavy" is actually kind of correct if you decode "heavy" as "it has a lot of mass". THe only thing peple didn't think of is that mass not only means weight in condictions of gravity, but also inertia. I personally think m that your thought experiment of trying to get the car moving in deep space is much more ilustrative of the phanomenon of inertia, than the actual car experiment ^^ On the other hand maybe I'm being too ritical now. The video might be a good reminder of the fact that "Hey! Inertia exists!" and that it is independent of weight, but still a function of mass.

[@trje246]

nice summation, that actaully made it heaps easier to get mah thick head round dude, cheers

[@floralbouqcake]

Hey can you make a video similar to this but velocity, speed and displacement. Yes i kinda understand the difference between them but i still confused.

[@youmaycallmeken]

When you load up your car with passengers and pack its trunk with heavy items, then when you drive you to need to realize it takes more to accelerate and to decelerate the car than before you added the extra mass. Inertia. Momentum.

[@toth1982]

Inertia is one thing, but the other is rolling resistance (which is mostly caused by friction and depends on weight and e.g. the surface of the ground). If you do not have this rolling resistance at all, you can apply a very small force by pushing and it will still start rolling. Inertia is a problem only if you want to deal with it very quickly. Rolling resistance consist the friction inside the moving parts of the car, but the biggest component it that the tires deform and get back to the original shape over and over again as rolling happens.

[@jv101]

Omg learned so much :--)👍👍👍⭐️🤔

[@huracan200173]

The guy at 1:11 made my day. FINALLY someone with gray matter!

[@jeffpee2708]

Hi @veritasium. I would like to ask for an specific measuring device that can be use to measure mass or the amount of matter in a substance. I think, one of the reasons for confusion between mass and weight is because of the measuring instrument used? Say for example, kg is measured using a weighing scale? I hope you will elaborate on my query. Thanks.

[@cetronics8211]

Hey, Kg is indeed measured in weight scale. but, in that weight machine they divide the input force by g(accelereration due to gravity). because F= ma and ma/a = m

[@jackl9068]

This is a big point

[@vebulous]

Best explanation of the "what is inertia" question. Ever.

[@phamthohongduong]

Omg. Great video!

[@elijahvigneault7579]

thanks this was helpful

[@justinmaxwell4199]

It finally makes sense..... Thank you.

[@iqbalmahmudmoon3965]

Two things i like about Australia is you and cricket. Love from Bangladesh

[@xxshevilxx]

That's clearer, thank you

[@definitionsinurdu2646]

Good explain my confusion is clear😊😊

[@areeb6703]

How is inertia of rest related for an object to move with constant velocity after overcoming friction?

[@aakarshansharma1120]

really nice you have cleared a big mess and its all sort out

[@Anytus2007]

@1veritasium Derek, I notice you really like using the idea of inertia. I think I understand why. You don't want to use mass because people confuse mass and weight (as you showed here). However, I have a degree in physics and I still don't really know what inertia is because I can't really see it or experience it directly, except through mass. Do you think there's a way we can make the mass/weight distinction and still say things like "cars are hard to push because they have lots of mass?"

[@-30h-work-week]

Thanks for replying, but I'm not sure I understand. :) I'd imagine I need more force to move the ball here, on Earth, than on the Moon. Unlike the car example, the ball wants to return to its original position as soon as it's moved, regardless how little. Since I'm the one stopping it to return, that should mean I'm lifting it up on that tiny vertical movement involved, right? Doesn't the power of how much the ball "wishes" to return depend on the gravitational force?

[@victorsubbiah6077]

both inertia and gravity plays the role in making the lifting & pushing hard. not just any one. in the case of this car, gravity is the major actor considering the mass of the earth against mass (inertia) of the car.

[@marko3296]

I know its not related but can you make a video about the double slit experiment and the uncertainty principle? No mater how much i read about it, still cant grasp the idea...

[@hopelansing7229]

Part 1 : I was wrong. There is something called rolling friction which is exactly what it sounds like. It is a force in the opposite direction of motion caused by the rolling tires on the ground. It depends on the surface and tire type so I looked up in a table to find a normal car tire on asphalt. The equation is : F=cW where F is the force of friction, c is the rolling resistance coefficient (looked up on table), and W is weight (m*g). Calculations in next post.

[@matthorseman706]

+Veritasium I would really like to see a video on the difference of momentum and inertia

[@mariavolk1418]

I FINALLY GOT IT!!! Thank you so much!