conceptual physics Mass Vs Weight

[@gabriellamusacchia]

WOW!! This was my Physics professor at City College! I am now a Ph.D. and Associate Professor of Communication Sciences and Disorders teaching Physics of sound and THIS GUY was the one who inspired me to go into science. I am so stoked to have found him again and am definitely going to show my class his great videos. Thanks Dr. Hewitt!!!!!

[@MakeScienceFun1]

+gabriella musacchia I found his videos twenty years ago when I first started teaching Physics. I'm in awe of his cartooning skills and ability to explain Physics so clearly!

[@BillfakingGates]

dude that guy is legendary

[@cradleofrelaxation6473]

You good should be proud to have great teachers.

[@yondertf2]

0:36 my man just drew a full illustration of a hand pulling a string in like 5 seconds

[@hectorpotnoodle6927]

My man drew it in 9 seconds 0:21 - 0:30

[@warshon123]

In just over 2 minutes, I am presented with an entirely new concept in physics that I've never encountered before. In that same short amount of time, it is explained and demonstrated so well that I feel I understand it to a high level. Magnificent teacher!

[@jc333jc]

This guy is a good teacher with great energy -no pun intended; plus having a passing resemblance to George Carlin can't hurt.

[@priitraag]

When the bottom string is pulled slowly, there is enough time for the force to spread equally between all the fibers of the strings. As the top string has some extra force applied by the ball, it will break first. If the bottom string is pulled rapidly, some fibers of the bottom string will break before being able to spread all the force to the second string. If wires were used instead of strings, the upper wire would break first in case of the rapid pull (force spreads quickly in metal).

[@aryansaeedi7618]

WOW! thank you so much. this was my question when video ended! Are you a physic major?

[@cradleofrelaxation6473]

Thanks 🙏

[@JackIsNotInTheBox]

Thats a very nice drawing! Doesn't anyone notice?

[@falsehoodbasher7240]

Yes!!!

[@deltagg2781]

He draws it very fast

[@sadraplyrics1]

@@falsehoodbasher7240 is a is a story about story about very a boy r the r8 of of f t7 and

[@supreetsahu1964]

If 1970's George Carlin starting teaching Physics.

[@syume16]

I wish all my teachers were as enthusiastic as him when it came to teaching their subjects.

[@mutlucantokat4079]

0:33 How did he draw a hand in such a short time?

[@justalazyguy.0_0]

That was really impressive

[@TTGLLGTT]

Who would check its neighbour when such an amazing teacher speaks

[@MissThoseTimes]

Paul Hewitt makes physics class come ALIVE

[@carultch]

Well, it's actually because of tension. Same reason any string ruptures. The inertia of the ball acts as a "tension insulator" between the bottom string and top string, delaying the accumulation of tension in the upper string.

[@falsehoodbasher7240]

Tension insulator huh...

[@RoBD7]

This man is an awesome teacher. I feel sorry for the guys sitting at last on the room...

[@koolsudeep]

i wish my physics professor was like that

[@chicoashgrove9794]

this is a good answer, not often explained in this demo (even though Hewitt is excellent) Do we know why the "tension insulator" is turned on with a fast tug whereas it is turned off by a slow gradual pull?

[@chicoashgrove9794]

Could you explain why a slow gradual pull is not affected by the inertia of the ball but a fast pull is affected by the ball's inertia. What specifically is it about a slowly applied force that seems to bypass the laziness of the ball and affect the upper string?

[@aryansaeedi7618]

I found this in the comments! Amazing explanation!! "When the bottom string is pulled slowly, there is enough time for the force to spread equally between all the fibers of the strings. As the top string has some extra force applied by the ball, it will break first. If the bottom string is pulled rapidly, some fibers of the bottom string will break before being able to spread all the force to the second string. If wires were used instead of strings, the upper wire would break first in case of the rapid pull (force spreads quickly in metal)." @Priitraag

[@carultch]

@@aryansaeedi7618 That's a great explanation. To add to this, the reason why "forces spread quickly in metal" has to do with the speed of sound in the material. Elastic response to a change in the structural loading of a material generally propagates near the speed of sound or at a significant fraction of the speed of sound. Speed of sound depends on bulk modulus (a measure of stiffness) and density. The stiffness to density ratio makes a material have a high speed of sound, like in aluminum and steel. A low stiffness to density ratio, like in rubber, means a slow speed of sound, and a slow propagation of elastic response.

[@darkmatter1289]

@@carultch can you answer this pls, same principle i think but cant figure out the difference If a massive object, such as a cinder block, is placed on the stomach of a person lying on the floor, and a second person strikes the cinder block with a sledge hammer, the person lying down, even on a bed of nails, is unhurt. HOWEVER, if the cinder block were not on the stomach, the person would certainly be injured. Explain.

[@carultch]

@@darkmatter1289 I didn't get a notification when you asked this question, but I can explain it. The hammer acting directly on the person, gives the person the full force from the hammer. But when the hammer acts on the cinder block, it has to first accelerate the cinder block from rest, before the cinder block can do anything to the person's stomach. Because the destination of the hammer's energy is shared between the block and the person's body, a lot less of it is directly applied to the person's body. The cinder block slows down the impulse, by first needing to accelerate, so that the force applied to the person's body is less. The same impulse is ultimately still applied to the person's body, just slowed down so that force is traded for time. The bed of nails is another matter entirely for why it works, albeit often part of this experiment, which has to do with more of your body being spread out over all of the nails uniformly, so that not any one nail gets you. You will also see that the head rarely rests directly on the nails, which is very difficult to get the head's footprint to uniformly distribute the weight. So the performer's head is either resting on something else entirely, or the performer wears a turban to cushion the support of their head.

[@gabssnake]

Awesome way to teach !

[@karisma-mcm]

The Bob Ross of Physics! Loved his textbook Conceptual Physics!

[@josuecell]

The professor draw a great picture in the board real quick!>.WOW!> great lesson too!..

[@gutpile59]

My neighbor was just as stoned as I was. Class of ‘77

[@MazDelaCerna]

absolutely amazing!

[@mellenstei]

abhijithero so why does lower string break when he jerks it ????????? it's because of inertia!!!!!

[@hectorpalacios5527]

You're never going to forget this.

[@bboydjoe]

see this is the shit we should be learning about in physics, conceptual stuff that actually make sense!

[@monicasilvanavillegasromer1349]

excelentes videos

[@Dyslexic-Artist-Theory-on-Time]

Neat video!

[@eyalgoldmann3154]

Sloppy explanation of the second part of the experiment. A better explanation is that by pulling on the lower string quickly, the ball is forced to accelerate downward, so the NET force on the ball is downward. This means that (tension in lower string + weight) is GREATER than tension in upper string. If the downward acceleration of the ball is GREATER than the free-fall acceleration (9.8 m/s/s) it works out that tension in the lower string must be greater than tension in the upper string. Good demo, but he's illustrating Newton's second law, not inertia.

[@navajasrs2402]

I wore almost that exact same outfit to highschool (salt and pepper jeans with a pink shirt) minus the snazzy gold chain in 1990.

[@DjangoFatt]

I can't wait to take this class

[@gigioneumatica]

so informal and so entertaining

[@TheOneAndOnlySame]

Mass is the delaying of force(s) due to mechanical constraints

[@falsehoodbasher7240]

How does this explain mass vs. weight

[@DJVARAO]

when he pulls down SLOWLY the string cord, the force he makes is ADDED to the WEIGHT of the ball. Hence, the top section of the cord experiences a total force = Fpull + Fball. When he QUICKLY pulls the cord down, the INERTIA of the ball makes it to stay in position, not making too much tension on the top side of the cord. Hence, all the force is on the bottom side of the string cord, and hence it snaps.

[@twinturbodan4389]

My teacher is making me watch all of his videos!

[@Arghira]

I love his excitement

[@MustangGTR2]

@gunblade64 definetely,may be they are overwelmed by math class

[@bahmanfarahmand4053]

Great

[@wmlfan9]

Another word for "inertia" is "lazy". I like that.

[@milosmihailovic8988]

Thanx!

[@Ben-qi2rc]

the Bob Ross of physics

[@sidharthserjy8984]

anyone knows how to find his full videos?

[@ericklopes4046]

Google Paul Hewitt

[@sidharthserjy8984]

Dude it isn't there

[@stevet6676]

Actually, my town library had a set of Hewitt courses on VHS tape (that's how old they are!) But, check around where you live.

[@63nbell]

@itsabomberscope No, he's the George Carlin of physics.

[@ಅಚ್ಚರಿ-ಸ8ಘ]

weight is the product of mass and g , while mass is total quantity of partilces

[@4fifty8]

@UCMolosser Ya. I dunno why I said that in my comment!

[@Mohsinkhurshid07]

Is there any one who have complete lectures of Paul hawit?

[@carultch]

Arbor Scientific sells DVD's of his lectures.

[@BABarracus6]

@itsabomberscope chuck norris teaching physics

[@goerizal1]

in a solar eclipse the moon is between the earth and the sun, subject to opposing gravitational pull from the earth and the sun. what happens to its weight?

[@carultch]

The fact that it is a solar eclipse is not relevant. The sun pulls on the moon by a greater amount than the Earth at all points in its orbit. The reason the sun doesn't steal the moon, is that the moon and Earth both accelerate together toward the sun. If you look at the moon's full year path around the sun drawn to scale, the moon's orbit is entirely convex, and never curves outward, because the Earth never overpower's the sun's pull on the moon. The Earth increases the moon path's curvature during a full moon, and decreases the curvature during a new moon, but the curvature of the path never faces away from the sun. Some of the gas giants do overpower the sun in the pull on their moons, and you get a concave-outward section of the trajectory every time the satellite passes through new moon phase, but this doesn't happen with the Earth's moon.

[@goerizal1]

@@carultch : i appreciate your taking time to answer but i have have to ask further although i suspect i maybe too simplistic but any way if the weight of a mass is dependent on the pull of gravity on it, should the moon's weight be somewhat less due to the opposing gravitational pulls from the earth and sun without any change in its mass? thanks..

[@carultch]

@@goerizal1 The moon's weight is nullified by the fact that it accelerates along with the net force of gravity acting upon it. No constraint forces hold it in place. Just like astronauts on the ISS who are weightless, even though the force of gravity on them is still about 90% their weight on Earth's surface. What you perceive as your weight, is really your assumption that the constraint forces acting on you oppose your weight. You cannot feel gravity, you can only feel constraint forces. If instead of weight, you mean force of gravity, then yes, the position of the Earth does vary the net force of gravity on the moon. During a new moon phase, the Earth subtracts from the sun's gravity, causing the moon to loosen the curvature of its path. During a full moon phase, the Earth adds to the sun's gravity, causing the moon's path to tighten its curvature. If you look at the path of the moon from the Earth-moon center of mass, you see the moon's individual orbit around the Earth. But if you look at it from the sun reference frame, you see that it is also orbiting the sun, just like the Earth. The moon weaves in and out of the Earth's orbit around the sun, as a consequence to the Earth's gravity.

[@goerizal1]

@@carultch :what about of bodies or masses on the surface of the earth - does their weights fluctuate accordingly as the earth move along its elliptic orbit bringing them closer or farther from the sun along the course of that orbit?

[@carultch]

@@goerizal1 The short answer: no. The longer answer: yes, but not nearly to the degree you immediately think, and we call this effect, the tidal forces. For the no part of the answer, the explanation is that most of your weight due to external astronomical bodies is nullified by the fact that you co-accelerate with the Earth. Both your body and the Earth receive a certain gravitational force per unit mass by virtue of position in the gravitational field. The sun's gravity on the average kilogram of the Earth is approximately the same as the gravitational force on the average kilogram of your body. This means you accelerate toward the sun along with the Earth accelerating toward the sun. And likewise, to the moon as well. An object in free fall has its weight nullified by the fact that it accelerates with the gravitational field, and the same thing happens with astronomical bodies in orbit. There isn't any non-gravitational constraint force to hold the Earth in orbit around the sun. For the yes part of the answer, the explanation is that the sun and moon pull at different strengths per unit mass on the Earth, depending on where in this field the target object is located. On the near side of Earth to the astronomical body in question, the gravity is greater than it is on the average kilogram of Earth. On the far side of the Earth, the gravity is less. The near side of Earth is pulled toward the source of gravity, and the far side of Earth lags behind the rest of Earth. This is why there are two high tides a day, once when the moon is at its apex, and once when the moon is directly opposite its apex. The moon's tides are about twice the magnitude of tides of the sun, because distance matters a lot more than mass. The moon is 2/3 the explanation of the tides, and the sun is 1/3 the explanation of the tides. Full and new moon phases enable the sun to assist the tides of the moon, and are called spring tides. Half moon phases cause the sun's tides to partially cancel the moon's tides, and are called neap tides.

[@saulorocha3755]

When you pull fast the the lower string, the upper one doesn't have the time to remember that it is already being pulled by the ball weight? Duh.

[@pryletoncyo]

Well, the ball has a lot off mass, probably. And I have a lot of mass. And I'm lazy, so I guess the ball is me, and the string is the interlocution, or the teaching, and the fist that pulls the string is the teacher. Better pulling strings than hitting me upside the head.

[@milosmihailovic8988]

Physic is supeeer!

[@4fifty8]

I think this guy explained the difference between mass and inertia... not mass and weight!

[@Deniz-xv9cb]

came from vsauce, not dissapointed

[@josephgeraci4511]

All i learned is how to break string.

[@artsolar]

because you did not pay attention

[@jdelco139]

Check ya neighbour!

[@Sly7de]

...an object at rest will stay at rest....

[@Jennamb007]

Physics Jesus!!!

[@TheRyanlabine]

bam bam bam harder harder harder

[@supremeon1]

another word for inertia is lazy ????

[@jpmorgan187]

the dictionary lookup for pedantic should redirect to this youtube video

[@pe16r02la0]

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[@ravi04318]

check your neighbor

[@phatboi973]

Lol this is funny

[@zeero62]

That didn't explain a fucking thing.

[@MrEbichan]

lazy

[@kgmansor]

lol wat a nerd