Conservation of Angular Momentum: Bullet and Door Collision Problem

Рет қаралды 18,499

2 жыл бұрын

Physics Ninja looks at a collision problem of a bullet and a door. Two cases are looked at and in each the final angular velocity of the door is calculated.
Conservation of Angular momentum is used in both cases.

Пікірлер: 37

@ryanphung3858 2 жыл бұрын

thanks for making these videos man! i like your thorough explanations

@sayanjitb 2 жыл бұрын

dear sir after the collision if I take the center of mass of the combined system (which is also 0.5 m away from the pivot) and calculate final angular momentum of this combined com w.r.t pivot (as a point particle 0.5 m away from pivot)i.e. I_com w= (15.01)*0.5^2*w_f, then in this way w_f is not coming as expected, why? please help!

@sujitiyer5436 Жыл бұрын

How did you determine direction of the pivot force on door?

@pramodsharma75158 Жыл бұрын

in second situation ,if we find the cofficient of restitution of collision we are gettimg it negative why?

@user-le3oy9gd2f 2 ай бұрын

when u considered energy, why did you only consider KE? wouldnt there be Gpe aswell since initially the bullet is in the air, and after the combined system is displaced?

@SouravPaul-xp2hx 9 ай бұрын

Hey what about mg which is the external force

@lilypieramici5510 2 жыл бұрын

Shouldn't the angular momentum initial be 2, not 20?

@AndyMBBallSkills 2 жыл бұрын

yes, sorry about that. The final answer for omega is correct. I must have misread my hand written notes when making the video.

@smileyface8294 2 жыл бұрын

hello, I have a momentum question, and i have no idea how to go about it. If I were to ask you would be able to help me solve it?

@PhysicsNinja 2 жыл бұрын

Reach out onlinephysicsninja@gmail.com

@Test-iv4pm 2 жыл бұрын

Do you have a lesson similar to this, but without the pivot point? That is to say, the bullet hits the door, and receives a certain amount of angular velocity AND a certain amount of linear velocity

@PhysicsNinja 2 жыл бұрын

Angular Momentum - Clay Puck and Stick Collision kzfaq.info/get/bejne/jK2lnK96mqndgYE.html

@Test-iv4pm 2 жыл бұрын

@@PhysicsNinja Thank you

@nkosinathimsimango5514 Жыл бұрын

@Physics Ninja can I please send you questions and then you do videos solving them

@user-eh8yk3hw6y 7 ай бұрын

8:05 Why omega finals are equal ?

@shivamraj04 Жыл бұрын

This really helped a lot Thanks

@loverboy9187 Жыл бұрын

can u tell me by gravitaional force is not doing external torque

@shivamraj04 Жыл бұрын

I think you misinterpreted the figure It is not a hinged rod but a door 🚪 as seen from top of the door(say from ceiling point of view) Gravity is acting into the plane of the figure And the torque due to gravity is being cancelled by hinge reaction Hope you understand

@loverboy9187 Жыл бұрын

@@shivamraj04 oh okay got it so if a force is parallel to axis of rotation then it does no torque

@yasinzengin3035 10 ай бұрын

In the next video of the playlist, the rod is not pivoted. And in that question, when the clay sticks the rod, the center of mass was changing. What's the difference with this problem? Why didn't we consider the changing center of mass if there is any change?

@PhysicsNinja 10 ай бұрын

In this problem there is a pivot so the rotation will be about this point. It’s an extra constraint on the problem.

@yasinzengin3035 10 ай бұрын

@@PhysicsNinja Oh, now I see. Thank you so much for the fast reply sir. Appreciated!

@mulatiedemis3501 Жыл бұрын

great 💪💪💪

@bluefoxf5963 2 жыл бұрын

How pivot produce external force? Is it due to centrifugal force?

@PhysicsNinja 2 жыл бұрын

It prevents the top from moving to right after the collision.

@bluefoxf5963 2 жыл бұрын

@@PhysicsNinja aah yes, i got it, thanks

@vaibhavgoyal6613 7 ай бұрын

But angular momentum is conserved for the moment just after the collision right bcoz after that there would be mg torque acting about the pivot

@PhysicsNinja 7 ай бұрын

Yes

@user-eh8yk3hw6y 7 ай бұрын

8:21 by 'That axis' do we mean the middle point -center of mass- of the door sir ?

@furkanerdogann 6 ай бұрын

no, he meant the pivot point because angular momentum is conserved at that axis. You can see that if axis of rotation passes through com of the door, its moment of inertia would be (1/12)MR^2

@osmanaltanyuksel1884 6 ай бұрын

Anladım teşekkürler

@NepaliQuanta Жыл бұрын

what does initial angular momentum mean .. initially bullet is travelling in a straight line.🤔 I got confused sir..

@PhysicsNinja Жыл бұрын

That is a great question. It’s weird but objects moving in a straight line can have angular momentum depending on the choice of origin. Angular momentum is L=r X p, but r depends on the choice of origin. I’ll post a short video on this next week.

@NepaliQuanta Жыл бұрын

@@PhysicsNinja waiting for that video sir ❤

@pramodsharma75158 Жыл бұрын

in first case e=.0005 and in secuond case e=.25