Relative Motion and Inertial Reference Frames

[@sunmoon88]

Thank you for speaking slowly and clearly unlike others in the profession of KZbin science presenters who seem to speak at the speed of light.

[@racinerobinson]

😂 very well said...especially considering the topic.

[@kritikasharma1264]

😅😅true Speed of light 😂

[@rikrishdevkota7655]

lol

[@Allan-et5ig]

Well, that's all relative! Kidding.

[@Alex-ns6hj]

relative to them, they're speaking very slow because they know the topic and know the story-line behind physics. We don't know it yet, so we can't possibly remember where every object is located along the way so we are going very fast lol.

[@starpravesh]

Those great animations must have taken a lot of time to animate. Great job.

[@ProfessorDaveExplains]

they take forever! but it's worth it :)

[@vasavikarnati6225]

Not good

[@ssancak]

@@ProfessorDaveExplains Hi Dave. May I use this as supplementary source in my physics class? While explaining the reference frame the animations that you prepared will make it much more clear for the students. Dr. Serkan Sancak (Ph.D. Physical Oceanography).

[@ProfessorDaveExplains]

yeah like just to show it to your students? of course!

[@ssancak]

@@ProfessorDaveExplains Sure, if we have time I'll play it in the class or just share the link of your video. I was already mentioning your channel within the "content approved" sources. Generally I don't trust youtube contents easily, some are full of mistakes. Keep up the good work! And thank you very much.

[@s_tnnd]

I'm a high school student and I came to this video because pf my Physics teacher. He already mentioned the video was great but I didn't imagine it that GREAT. Professor Dave, you have a new great fan! You actually have solved all my doubts I had with this term. THANKS!!!!!!

[@MrTunapie]

WOW!! This guy is very good.. I been struggling with this for days, reading a lot and getting more confused. He made it simple to understand. Why cant more teachers do this???

[@avismuse7674]

Please explain me

[@u235u235u235]

there's no way you did your assigned reading. if you really did your assigned reading and you're still confused then science is not for you.

[@tabassumfaisal3211]

u235u235u235 some people are visual learners uknow

[@Freyia935]

@@u235u235u235 wow what a stubborn view, you are more deserving of being told that science is not for you.

[@u235u235u235]

@@Freyia935 ?

[@blaster-zy7xx]

"The Milky Way galaxy is moving through the universe at 230 km/sec" Relative to what?

[@ProfessorDaveExplains]

just other galaxies, i believe.

[@harshraj4178]

that means its velocity is different with something we kept as stationary there

[@milodjilodj]

But they also move... How to know the absolute velocity in space/everything/existence?

[@milodjilodj]

Do we know if the space/background is not affected by the gravity of just us, or something much bigger that could be pulling us too?

[@vpheonix]

""The Milky Way galaxy is moving through the universe at 230 km/sec" Relative to what?" All galaxies are moving away from the center of our universe, so the velocity pf 230km/s would be relative to the center of the universe.

[@etriuse4354]

I love the way the car just honks at you cuz you're explaining physics in the middle of the road

[@beepinlim8270]

When we stand still relative to the object, we are taking it's reference frame. Inertial reference frames are the frames that does not accelerate relative to other inertial frames. An easy way of testing inertial frames: take any object and release it in mid-air. If the object stands still, your frame is inertial.

[@rusbunnin3992]

Prof.Dave yo rock Remember, you could be the best teacher the humanity has ever seen ... Cause ya shrunk a hour class into 6 mins and still it is well understandable

[@jaywoods4095]

DUDE THIS WAS THE MOST SIMPLEST EXPLANATION ever, many thanks!!!!

[@harrybarodawala3588]

Another way I like to think of it is that when you are on a train and are moving away from the platform, it looks like the platform is moving and the train is staying still, so the train and the platform are both the inertial reference frame.

[@kuelewa332]

None of the explanations in my native language helped me understand the topic and this video did help me. Thanks, Professor Dave.

[@hexaprime5445]

You explain better in 6 minutes than a book does in 1 week

[@celes-p]

You just explained the same concept in 6mins that took my physics teacher 3 months. It was so simple to understand?????

[@fkncompton7124]

This was really confusing in the textbook, but this video made it infinitely easier to understand, thanks

[@Igreatlyadmirecats]

Just watched this video yesterday for 9th grade Physical Science.

[@colorx6030]

Holy crap never have I understood inertial reference frames as I do now. Thanks a lot for this! Every explanation of inertial reference frames I saw were so complicated and confusing to understand.

[@jakesparrow5716]

Videos like this deserve a love button. Like just doesn't express the gratitude.

[@joeybasile545]

Visualizations are very important in learning. Thank you for the animations - they drilled the concepts home.

[@gokucrafter9456]

Brilliant video, only one mistake is that Earth is not an inertial frame. Rather, Earth is a non-inertial frame of reference. A frame of reference is an object or a system that is used as a standard for measuring the speed of objects. A non-inertial frame refers to any reference frame that is accelerated with respect to an inertial one.

[@ProfessorDaveExplains]

We can approximate it as an inertial frame, it works out quite nicely.

[@gokucrafter9456]

@@ProfessorDaveExplains Yep I did a research and earth can be both depending on our view and you're right that we approximately use earth as an inertial frame

[@giorgixyz1909]

GOSH, I've never seen anyone explained the concept so clearly.. Concepts puzzled me for years finally gotten solved! Thank you so much.

[@marijandevic2888]

The best intro ever

[@abigailmatthews8996]

You explain really well and make it so easy to understand.

[@lalitperuliya5742]

Seriously..mind blowing explanation 😀

[@therealemtothebee]

I literally just now understood how time is relative in spacetime and how events can be perceived differently by different observers in that context. thank you

[@sapphire5144]

this video was so so helpful! you make learning the topic easier cause you speak slowly, have colorful pictures/animations to illustrate your explanations, and emphasize definitions. thank you for packing my 2 hour physics lecture into 6 minutes!

[@vincentcooper9139]

Your explanations and diagrams of basic concepts in physics are wonderful. I have used them to teach my children.

[@JeremiahJamesMusic]

Solid explanation! Thank you

[@acesw6124]

I really like the element of history included in teaching to show how humanity discovered something abd how we know it to be true . Without understanding history certain parts of the present are not comprehensive. I recently watched Veritasiums video on depressed cubics and how to solve them

[@MoonKing-ih1pv]

3:36 the ball does have the horizontal velocity of the train... The important point is you do too... So with respect to you... The ball remains at rest.. correct me if I am wrong..BTW you help us a lot man!🥂

[@DepressionAlgorithm]

Simple, straight forward and with illustrations that make sense. Excellent video. Thanks.

[@yssacnton95]

Thank u, it's been days I have been watching one video over other, this resolves my problems

[@hammadsafder5435]

Excellent explaination 🙌

[@stefanzhu8219]

This is way better than Crash Course or Khan Acadamy!! Thank you so much!

[@ProfessorDaveExplains]

thanks for the kind words! i aim to please :)

[@AliAli-pj8vp]

exactly

[@oliverbeck6839]

@J lol I think this guy is like a science teacher for retards, khan academy is way better but if your slow in the brain you might not be able to follow along, this guy might suit you better in that case

[@snoochen]

Because Khan Acadamy is wrong. He should go back to academy. Kahn is giving misleading information and incorrect.

[@b1042]

i think khan academy and this video are both very helpful in different ways.

[@shay3355]

his intro is probably the best intro I've ever seen

[@phu2110]

This guy managed to explain something my lecturer took an hour to do in 6 minutes

[@victorychibuike2049]

wow, I won't be needing another video anymore. Hallelujah

[@aniketghoman8412]

You nailed it Professor Dave..loved it.

[@katarinalima8082]

I FINALLY UNDERSTAND THIS THANK YOU SO MUCH IT'S BEEN YEARS

[@hadihairi1622]

I read few Physics books to understand this and you explains this so well ! Thank you !!

[@alyaaathirajasmine8716]

the best explanation yet. thank you!

[@rachitaurora]

Thank you Professor Dave!

[@mxkep]

I would recommend those who are only being introduced to this concept to take a look at the amazing properties of Einstein's Relativity. Great videos! Love your channel!

[@sujathan4116]

Woooh bro people are seeing this to learn about relative "motion"(as in just mechanics) not time dilation,space time etc

[@shreyaroy457]

Thanks sir . I can now understand the inertial reference frame 😀😀

[@josephreagan9545]

Great video. Small correction Gallaeo didn't get in trouble with the church for saying the earth revolved around the sun. He got in trouble when he tried to teach that the moon had nothing to do with the tides on earth, which we know to be false. (My church still should have stayed out of the matter, but the point is that he didn't get in trouble for teaching a theory about the sun but for teaching an incorrect theory about the tides as truth.)

[@vaishnavi3744]

you are simply amazing ..... was tired and confused after watching so many contents....but you made it all easy ..... love from india **** sir

[@bikrammondal514]

I like professor Dave, he is so pure and positive man!!!❤️❤️

[@subashpriyatharsanvlogs9831]

Can you please explain in details how a fly soar around very casually inside a car that is going around let's say 120 km/hr.? I mean the flies don't go up and down like the ball you showed here in animation, they are going all the ways and up and down and right and left? It will be much helpful.

[@Wazxa0p]

2:09 TANK U SIR, the damned book told me two tests to run to see if the reference frame is inertial, talking about some mumbo jumbo when it's this simple to explain.

[@riveratomwaters]

Let's talk about absolute position and reference frames. Positions that physicists calculate in each reference frame is a partial and ultimately incomplete calculation when it comes to position - in fact there is absolute position and all observers from each reference frames can agree on position if they have the proper equations gauges, sight, and instruments of all kinds. Absolute position is calculated by taking into consideration all the reference frames or the total reality of say a ball bouncing on a moving train. All viewers from every reference frame can agree with equations a gauges etc. As stated. For instance - a ball bouncing on a moving train - observer 1, a person standing at the side of the train tracks - observer 2, a person in outer space that is motionless. The person that is motionless in space sees all reference frames and can calculate absolute position quite easily - but infact they can all read or detect all reference frames to to the calculation, like the person on the train with a telescope that sees the person motionless in space, has a compas, has a speedometer, sees position outside looking through the window and all equations. The fact is they will all agree on position if the calculation of position of the bouncing ball is completed fully with all the reality behind the bouncing ball - all reference frames - which can all be detected and calculated- that is absolute position. Everything else I like to call a relative position - which ultimately are incomplete calculations of actual or absolute position.

[@frozengrenadier3071]

I appreciate your explanation. I learned a lot today.

[@jebastingnanaraj8452]

my confusion is cleared.thank you professor.

[@Allan-et5ig]

Professor Dave Explains - Two ping-pong players on a train going 60 hit the ball to/fro at 6 mph. A stationary observer near the train not within their inertial frame sees the game as the train flashes by. To he/she stationary observer, the ping pong balls are moving 60 mph. And NOT 6 mph...as the observer is not part of their inertial frame. Correct?

[@Arun_Kumar_x86]

i think the guy on ground sees the ball at 65.99 mph

[@Allan-et5ig]

@@Arun_Kumar_x86 You're not terribly bright, are you?

[@carultch]

@@Allan-et5ig You never said that the ping pong gameplay was aligned with the track of the train. The following answer assumes this is the case. The stationary observer would see the ping-pong ball moving at 66 mph and 54 mph respectively, while the players would see it moving at +6 mph and -6mph. At these speeds, relativistic effects are insignificant, and it is OK to consider velocities to simply add. If you had a ping pong table perpendicular to the axis of the vehicle, you'd have to add up perpendicular velocities according to the pythagorean theorem. This would more likely be the case on a cruise ship, since the vehicle is a lot larger to fit a pingpong table.

[@msudheendra7192]

My favourite science teacher forever

[@davida6146]

This was the best explanation for this phenomenon! Thank you

[@EmerxldSpeed]

Really appreciate how you put in so much effort in the animations to make stuff way easier for us 🥰

[@Jack__________]

If you were born on a plane (600 mph ((relative to the ground)) and 10,000 m altitude at the equator) that never had to land, what would the difference in age be between someone traveling east and someone traveling west in 50 years?

[@NikoGustafson]

Beautiful, easy to understand, and efficient explanation! I also appreciate your enunciation. You are incredible! Thank you for creating such phenomenal educational content! 💓💓

[@howiestillgamez5326]

just wondering, I have been told that the speed of light is absolute, but relative to what? it doesnt speed up if the light is coming out of a headlamp of a moving vehicle, but what is that relative to. If the speed of light is absolute, then could it be at a different speed in a galaxy that is moving at a different speed relative to us?

[@KevinKuzel-zv5gh]

Thanks for this! Great content!

[@undyingshithead2182]

Wow, this is well made. Good job, Professor Dave.

[@kjaideep]

Thank you sir I was very eager to learn this my i completed 90 % of my internet but finally I learned because of u

[@kritikasharma1264]

OMG !! You seemed to be like a mirror for me which displayed everything and made my views vast........... Just Thanks sir 🙏🙏Love from India ♥️

[@kritikasharma1264]

Hope could meet you sir

[@francescoiaia2o]

The intro creeped me out, but still subscribing for teaching topics very important for the humanity.

[@muhammadmuhsinmohdrazib216]

simple yet understandable explaination for a very complicated topic.....thank you

[@melisapham6627]

Excellent explanation! My book was not very helpful for this section and basically just gave me an equation without going into almost any detail.

[@Earth1960]

3:00 So 2 wrongs make a right, got it. Seriously though, doesn't the work done by the car's engine distinguish between the motion of the car and its surroundings? The surroundings aren't burning petrol to move 100km/h in the opposite direction? And when the car is parked, so at rest relative to its surroundings, it's not burning fuel.

[@trustkibou]

Fantastic, thank you! I was struggling to understand the textbook's explanation of an inertial frame, and you described it perfectly! :)

[@Uri1000x1]

It's an unaccelerated frame, one attached to something that's not feeling a force and thus accelerating by F = ma. The word frame means there's a coordinate system used to specify locations within the frame. Maybe the Earth's frame has coordinate x,y,z = 0,0,0 at Earth center of if you like 0,0,0 is where you are standing on the surface.

[@Owais-Ali]

4:35 what if the ship is moving with an acceleration?

[@omricohen111]

Dear man I appreciate your work, I would love if you would make a video about energy in reference systems

[@tb2748]

What would the free body diagram of the ball look like when it is in the air (when thinking about the example with the train)? Is there a horizontal force that acts on the ball in the direction that the train is also moving?

[@ffhashimi]

Great explanaition; you make things look much simpler!

[@yapzhilin9857]

Thanks so much for the super good explanation!

[@SasukeUchiha0330]

Thank you very much, my "PHD" professor briefly covered inertial frames but this video was able to make up for her incompetence!

[@terrancepage9163]

thanks so much for this! back to the textbook reading now that I understand this part!

[@FacePeelN]

“Officer, I travel in absolute velocity hours”

[@dragonore2009]

This went over flat earthers heads. They need the version where you have a bunch of memes.

[@popeyelegz]

The ball will fall directly below from where it is dropped only as long as it has the same forward momentum of the ship. If the ship were, let's say, 15,000 feet high, the ball would lose forward momentum as it fell and miss the bull's eye as the ship moved forward. The forward momentum dissipates when it is not touching anything else that's moving.

[@ProfessorDaveExplains]

No, it doesn’t.

[@popeyelegz]

How do we know, since all other velocities are relative? Isn't it the same as throwing up a ball in the back of a moving truck? If you throw it up high enough, it will land outside the truck.

[@popeyelegz]

The example I remember is watching a special min the 90s about a guy in an observatory that shines a laser onto a mirror on the moon. He said that they have to calculate a change in position in the laser because, by the time it bounces off the mirror and comes back to the earth, the earth has moved enough that the laser comes back to a different position.

[@thedigitalmelon7326]

@@popeyelegz I know this is a year late but the ball would loose its forward momentum because of air resistance. In an enclosed space where the air is stationary relative to the frame of reference the ball would fall straight.

[@heyvatss]

Much much better than any of the other videos😘😘

[@johnmichaelsto.domingo3611]

thanks prof dave. it helps me a lot. looking forward for more video tutorials.

[@Priya77772]

Sir how can I show that an inertial frame of reference has constant velocity...?

[@omawasthi2080]

by constant acceleration from newton's inertia law

[@carultch]

Definition. That's what defines an inertial reference frame is constant velocity. And in general relativity, zero gravity is also needed to define it as an inertial reference frame.

[@Basimahmaso]

I like how the video isn't long

[@Arun_Kumar_x86]

Hello, I have a big doubt I think the part at 4:26 is wrong. From the point of view of the fish, the ball will fall in a vertical motion and for the guy who dropped the ball (Galileo Galilei), the ball will move backwards. I think this happens instead of the fish seeing the ball dropping in a parabolic path. Is this correct or am I mistaken?

[@princearhinful4954]

Nice introduction I love it

[@EmerxldSpeed]

But initially you said that the observor sees the ball taking a parabolic path because the ball had all the horizontal velocity(of the train) and then later on you say that the ball and the person throwing the ball up dont undergo motion but their surroundings do and hence the ball falls vertically downwards and has a vertical velocity only, kindly clear my confusion.

[@ryani.8916]

This was so helpful

[@ballerstalin5346]

3:10 Sir this example is explained by Stephen Hawkings in Brief History of time....you really are wonderful.

[@agustinsamanthajoymisagal2858]

How do you describe the motion of a coin dropped by a person in a moving car under the following conditions: a. in a reference frame of the car ; b. in a reference frame fixed on the Earth?

[@carultch]

In the reference frame of a car, the coin will fall straight downward. In the reference frame fixed on the Earth nearby the car, the coin will fall in the second half of a parabolic path, with its vertex at the top where the coin is released, and concave-down curvature.

[@Aer01614]

By the logic discussed in this video then isn’t it perfectly legal to say that the earth is the center of our solar system and the sun does revolve around us if we take our planet as the inertial reference point?

[@ProfessorDaveExplains]

In the context of assigning a reference frame to perform a calculation, I suppose so. But in the greater context of simplification, it makes things pretty absurd.

[@nodeUser]

Not exactly...

[@carultch]

Of course it is legal to say it. We have freedom of speech in the USA, and it is legal to say just about anything, regardless of whether it is factually true or not. And despite that meaning that proponents of crazy conspiracy theories have the freedom to spew their absurd ideas, I consider this a good thing for a society and support freedom of speech. You could define Earth as stationary, and determine the kinematics of everything else in the solar system relative to it, as Ptolemy did in his model of the solar system, but it makes your math a lot more difficult, and it distracts you from understanding why it works. Earth as a reference frame wouldn't qualify as an inertial reference frame because it is accelerating, and you'd have to introduce pseudoforces to account for this.

[@shalukumari705]

It's really a good one , specially the animations were more relative to the frame of understanding 👍

[@jebastingnanaraj8452]

Hi professor ,I have one doubt the Earth moves faster nearer to the sun and moves slower farther to the sun the velocity is not constant it is varying between some values so from your point of view Earth is an inertial frame of reference but the condition for inertial frame of reference it obeys Newton's I law (constant velocity) . please explain?.I am confused.

[@ProfessorDaveExplains]

good question! we approximate earth as being an inertial frame of reference, but you're right, in the strictest sense, it isn't one.

[@vinnichugh7539]

Explained so well! Thank you for this video. Keep uploading such videos

[@arthurwieczorek4894]

The ball in the train business. This is what I don't get. It seems that the ball in the box-car frame of reference is traveling a shorter distance than the same ball from the rail side frame of reference. Maybe I get it now. Each observer has a timer of the throw. Both clocks will read the same time. So the rail side observer sees the speed of the up and down motion plus the speed of the inertial motion.

[@hariharanas368]

Thank You Mr. Dave

[@godlyvex5543]

I wish someone could explain how this relates to the portal paradox. I am confident that the portal moving towards a cube is the same as the cube moving towards the portal, but I just don't know how inertial frames of reference relate to environments on both sides of the portal. Why is it that an object only switches inertial reference frames after going through the portal?

[@swapnilislamarnnya2725]

nice explanation , thanks bro

[@whoisadesh2]

All of a sudden an alien starts falling onto your local supermarket

[@ebobab9564]

So to my understanding : The ball falls ''straight'' down in a train or whatever because it has the same speed as the train, and upon leaving my hand, it basically continues flying forward with the trains speed but due to the train having the same speed it appears to just fall straight down, right?

[@ProfessorDaveExplains]

yep i think that sounds about right!

[@mahadevprasanth1697]

Thanks for the vid

[@harshraj4178]

NO the only horizontal component of velocity is same as the velocity of train

[@mateiacd]

The ball falls ''straight'' down in the train only because the train is not accelerating.

[@sorestarbing3978]

Thank you Prof. Now I got a bit understanding in relativity (still studying)

[@dylanevans7529]

The Weird Thing is, if you asked the outside observer what path the ball took, they'd say up and down, because we'd automatically and subconsciously assume the reference frame of the person we're asked about.

[@alialemi4443]

thank you Dave