I aint gonna lie sir, so many times have I wanted to drop out of physics but your videos have saved me time and time again. esp. with this pandemic its real hard to focus, but ur videos always make me laugh and keep me interested. tbh prolly would be failing my physics class it it weren't 4 u... trynna give u all the adsense money cuz u deserve it king 😊😊😊😊😊😊😊😊
Mr. P! Thanks so much for your videos, my whole physics class loves your work (you should and will someday have hundred of thousands of subs). What is the best way for us to study for the AP Physics I exam? We are a bit behind, and are only learning about rotational motion, simple harmonic motion and Circuits and stuff now... Are we doomed? What's the best way to catch up and be most efficient with our time?
You are not doomed. I remember many years when I taught AP Physics B and would end up doing the last 4 chapters in one week. It will work out. The most efficient use of your time is probably to work through old AP exams. This will help you to learn more about the exam and to identify deficiencies you have. Then you can concentrate on making sure to study that which are struggling with. Best of luck in May!
Any chance you could help me out by doing what I ask people to do in the following video? bit.ly/2y4tOCA It would be a great way to show your appreciation!
Hope you'll get some ladies in your class ;) ! Thanks for your video - pretty helpful! I was looking for verbal/visual explanations of all this angular momentum conservation stuff for elementary students, but the very mathy equations are good for future reference
To move into the centre of the merry go round the child has to overcome its centrifugal force, and this centrifugal force is dependent on the radius of the merry go round, means the centrifugal is constantly changing while the child is moving closer to the centre, so we can also find work done with the centrifugal force expression, need to do integration though. 🤔 Good video sir!!
Thanks! Though I do not generally work with a "centrifugal force" because it is a fictitious force and does not really exist. I do recognize some people do work with it, however, I find that it confuses students more then helps them learn.
What if it started out at zero completely still, then the child started running on the wheel so it started spinning under their feet, then jumped over and landed on the other side of the wheel where it was moving in the opposite direction, so when they landed the wheel was now moving in the same direction as the child?
Mr. P, I am taking AP Physics 1 and AP Physics 2 this year. Which is a good site to study AP Physics 2? We haven't even completed AP Physics 1 yet. I think will start AP Physics 2 in February and complete the course 2 days prior to the AP tests. My school's policy is for the students to take both Physics 1 and Physics 2 together or not taking either.
@@ajayharilal3120 The force of gravity of the child DOES cause torque. The reason we don't need to consider the torque due to the force of gravity, is that there is an additional torque in the reaction of the axle/bearings that support the merry-go-round. The bearing/axle system only enables a vertically oriented axis of rotation of the merry-go-round, which an aircraft pilot would call yaw. Any torque that attempts to cause a rotation other than a yaw, which would be called either pitch or roll, would be counterbalanced by a reaction torque in the axle/bearing. The merry-go-round is free to yaw, but is constrained against pitching or rolling. Imagine what would happen, if instead of an axle, we had a ball and socket joint at the center. The torque from the child's weight, would cause the merry-go-round to tip downward toward the child.
Rotational kinetic energy is the sum of the work done by torque. If the rotational kinetic energy increases then there must have been a torque applied but your premiss is that no torque is applied. I guarantee that if you measure this system in real life, you will confirm that angular energy is conserved. BTW: contradicting the conclusion of a logical argument is directly illogical.
@@mrwaffleman8732 Please stop the character assassination? The demonstration is wrong and I think the students deserve to be taught properly how things work.
There is a torque applied in this problem, just not a net external torque, assuming an ideal bearing of the merry-go-round and no air drag. A torque pair between the child and the merry-go-round will occur, which will add up to zero net torque on the system. The reason this torque pair will occur, is as a constraint force against the Coriolis effect. Suppose the child follows the straight handlebar that follows a radial path. On a stationary merry-go-round, a child could walk this path, and only need a radial force to do so. But when rotating, the child will need to apply tangential forces on the handlebar and platform, in order to maneuver along the radial line. These tangential forces are what causes the torque on the platform, that enables the whole system to speed up when the child moves toward the center, and slow down when the child moves outward. Due to the fact that these are forces internal to the system, the forces in the interaction pair are equal and opposite, and don't add up to causing any net torque on the system, which is why we expect conservation of angular momentum to apply. There is work done on the system via the human forces that the child applies. The energy does come from within, so the total energy of the system would remain constant, if you accounted for all the chemical energy in the child's metabolic system. The reason the mechanical energy can increase, is that energy enters the mechanical domain by the non-conservative human forces from the child. There can be work done without a net external torque. There also can be net external torques applied to a rotating system, without work done, such as in gyroscopic precession.
@@shailkumarjain Agreed with nothing wrong with leaving critical comments. I've responded to the points John has raised in his original post of this comment thread. Note that John has an agenda to discredit the concept of conservation of angular momentum. There is a kernel of truth to his claim, because he did an experiment that didn't produce the speed increase predicted by conservation of angular momentum, when decreasing a rotating object's radial position. But what he is missing, is unintended external torques, caused by lack of counterbalance, friction, and drag. Experiments that better control for unintended external torques can produce results that are more consistent with conservation of angular momentum, than conservation of kinetic energy as John alleges should apply instead.
I aint gonna lie sir, so many times have I wanted to drop out of physics but your videos have saved me time and time again. esp. with this pandemic its real hard to focus, but ur videos always make me laugh and keep me interested. tbh prolly would be failing my physics class it it weren't 4 u... trynna give u all the adsense money cuz u deserve it king 😊😊😊😊😊😊😊😊
Thanks a lot for great explanation
Can you explain thermodynamics class 11
Mr. P! Thanks so much for your videos, my whole physics class loves your work (you should and will someday have hundred of thousands of subs). What is the best way for us to study for the AP Physics I exam? We are a bit behind, and are only learning about rotational motion, simple harmonic motion and Circuits and stuff now... Are we doomed? What's the best way to catch up and be most efficient with our time?
You are not doomed. I remember many years when I taught AP Physics B and would end up doing the last 4 chapters in one week. It will work out. The most efficient use of your time is probably to work through old AP exams. This will help you to learn more about the exam and to identify deficiencies you have. Then you can concentrate on making sure to study that which are struggling with. Best of luck in May!
@@FlippingPhysics Thank you, Mr. P for the well wishes and advice. I love the work you're doing. Thanks for everything you do.
Any chance you could help me out by doing what I ask people to do in the following video? bit.ly/2y4tOCA It would be a great way to show your appreciation!
Hope you'll get some ladies in your class ;) ! Thanks for your video - pretty helpful! I was looking for verbal/visual explanations of all this angular momentum conservation stuff for elementary students, but the very mathy equations are good for future reference
Thank u sooooooo much Bo 😁
THANK YOU SIR.
YOU ARE WELCOME!
Any chance you could help me out by doing what I ask people to do in this video? bit.ly/2y4tOCA It would be a great way to show your appreciation!
To move into the centre of the merry go round the child has to overcome its centrifugal force, and this centrifugal force is dependent on the radius of the merry go round, means the centrifugal is constantly changing while the child is moving closer to the centre, so we can also find work done with the centrifugal force expression, need to do integration though. 🤔 Good video sir!!
Thanks! Though I do not generally work with a "centrifugal force" because it is a fictitious force and does not really exist. I do recognize some people do work with it, however, I find that it confuses students more then helps them learn.
What if it started out at zero completely still, then the child started running on the wheel so it started spinning under their feet, then jumped over and landed on the other side of the wheel where it was moving in the opposite direction, so when they landed the wheel was now moving in the same direction as the child?
Merry go round is dangerous ☹️
Mr. P, I am taking AP Physics 1 and AP Physics 2 this year. Which is a good site to study AP Physics 2?
We haven't even completed AP Physics 1 yet. I think will start AP Physics 2 in February and complete the course 2 days prior to the AP tests. My school's policy is for the students to take both Physics 1 and Physics 2 together or not taking either.
What about the force of gravity on the child? Doesn't it cause torque?
No it doesn't because that's in the vertical direction and affecting both the child and the wheel so it doesn't have an overall effect
@@ajayharilal3120 The force of gravity of the child DOES cause torque. The reason we don't need to consider the torque due to the force of gravity, is that there is an additional torque in the reaction of the axle/bearings that support the merry-go-round. The bearing/axle system only enables a vertically oriented axis of rotation of the merry-go-round, which an aircraft pilot would call yaw. Any torque that attempts to cause a rotation other than a yaw, which would be called either pitch or roll, would be counterbalanced by a reaction torque in the axle/bearing.
The merry-go-round is free to yaw, but is constrained against pitching or rolling. Imagine what would happen, if instead of an axle, we had a ball and socket joint at the center. The torque from the child's weight, would cause the merry-go-round to tip downward toward the child.
👍
"Everybody brought mass"
*Doubt*
Ummm, this is a joke in case you think this is a question.
Ya I'm gonna fail my exam today :'(
I hope it went better than you thought it would
Rotational kinetic energy is the sum of the work done by torque. If the rotational kinetic energy increases then there must have been a torque applied but your premiss is that no torque is applied. I guarantee that if you measure this system in real life, you will confirm that angular energy is conserved. BTW: contradicting the conclusion of a logical argument is directly illogical.
hi my name is john and I leave critical comments on physics youtube videos made for high schoolers
@@mrwaffleman8732 Please stop the character assassination? The demonstration is wrong and I think the students deserve to be taught properly how things work.
@@mrwaffleman8732 nothing wrong in leaving critical comments. Specially in science.. If its correct, no body can deny it.
There is a torque applied in this problem, just not a net external torque, assuming an ideal bearing of the merry-go-round and no air drag.
A torque pair between the child and the merry-go-round will occur, which will add up to zero net torque on the system. The reason this torque pair will occur, is as a constraint force against the Coriolis effect. Suppose the child follows the straight handlebar that follows a radial path. On a stationary merry-go-round, a child could walk this path, and only need a radial force to do so. But when rotating, the child will need to apply tangential forces on the handlebar and platform, in order to maneuver along the radial line. These tangential forces are what causes the torque on the platform, that enables the whole system to speed up when the child moves toward the center, and slow down when the child moves outward. Due to the fact that these are forces internal to the system, the forces in the interaction pair are equal and opposite, and don't add up to causing any net torque on the system, which is why we expect conservation of angular momentum to apply.
There is work done on the system via the human forces that the child applies. The energy does come from within, so the total energy of the system would remain constant, if you accounted for all the chemical energy in the child's metabolic system. The reason the mechanical energy can increase, is that energy enters the mechanical domain by the non-conservative human forces from the child. There can be work done without a net external torque. There also can be net external torques applied to a rotating system, without work done, such as in gyroscopic precession.
@@shailkumarjain Agreed with nothing wrong with leaving critical comments. I've responded to the points John has raised in his original post of this comment thread.
Note that John has an agenda to discredit the concept of conservation of angular momentum. There is a kernel of truth to his claim, because he did an experiment that didn't produce the speed increase predicted by conservation of angular momentum, when decreasing a rotating object's radial position. But what he is missing, is unintended external torques, caused by lack of counterbalance, friction, and drag. Experiments that better control for unintended external torques can produce results that are more consistent with conservation of angular momentum, than conservation of kinetic energy as John alleges should apply instead.