Recent content by Game_Of_Physics

Is there any difference between the field lines you draw when one mass approached another mass and when two electrons approach one another? If there is no difference, does this mean field lines can't be used to predict the forces both particles feel?

Thanks! And if the question had not said to assume that the ball slips during the collision, how would one go about solving the subsequent motion of the ball? If it doesn't slip during the collision, does that mean it no longer receives an impulse parallel to the wall? Would you be able to...

Here is the quote from the book: "The problem refers to a change in angular velocity of the ball, so it is presumably not safe to assume that the ball is not initially rotating (and in fact if the ball were not rotating, it could not skid against the surface so the angles θ and Φ would be...

That's what it says, and as you suggest, this seems very counter-intuitive. The solution is from a book by a Cambridge professor though so I was reluctant to question it. Could it be a mistake?

An elastic spherical ball of mass m and radius a moving with velocity v strikes a rigid surface at an angle θ to the normal. Assuming the ball skids while in contact with the surface, the tangential reaction force being a constant fraction μ of the normal reaction force, and assuming the...

Ah...yes that's a good point! But then given that is the case, you could in theory have an impulse between an object colliding with another object, where the collision time is long due to a "small spring constant". In this case the force against time graph would be a line with a lower gradient...

If one ball collides with another stationary ball completely in-elastically, then the deceleration of the first ball and the acceleration of the second would be slower due to the increased contact time. For example compare dropping a tennis ball and its collision with the ground with that of a...

For the collision time to be infinitesimal it has to be elastic though doesn't it?

Oh...but surely it could just as easily not be a great enough force do achieve this. I mean what if the ball has only a very small angular speed?

But that is what your diagram suggests? You have drawn R1 greater than R2.

Yes that it was I meant to say. Okay, I see your point. Actually the question itself does not mention any such constraint, only the mark scheme I have be given by my tutor. What if the cylinders are on earth? Wouldn't that mean the cylinders do not necessarily leave the surface, because the...

Okay yeah, I think I follow. But that isn't conserving angular momentum is it? If the first cylinder starts with ω and ends with ω/2, whilst the other starts with -ω/2 then the system starts with angular momentum ω and ends with angular momentum 0, and so it isn't conserved.

Why are they equal in magnitude? You do not need no have vertical motion for them to have different reaction forces from the ground?

For the perfectly rough cylinders we have tangential forces acting on the cylinders. Assuming that they remain in contact with the plane at all times, this changed vertical force on each cylinder requires the balancing normal reaction force from the plane to change. Before the collision it was...

There is also an impulse from the ground on the first cylinder, causing a change in the angular momentum of a larger system including the surface, and therefore angular momentum isn't conserved.