Recent content by llandau

1. An elevator is moving upward with constant velocity V. We consider a frame of reference fixed to the elevator. Since it is not accelerating, our system is equivalent to, say, a frame of reference fixed to the ground (there are no inertial forces). Now, we are inside the elevator and let an...

You have been helpful, thanks (I believe you lost an M, but it really doesn't matter).

How to calculate gravitational potential inside a homogenous sphere of mass m? I am curious because I had to solve the classic problem of the tunnel through Earth and wanted to generalize when the tunnel is not a diameter.

You are right, it is straightforward, I should have given it more thought. Thanks, anyway.

Given an elliptical orbit, if I know all parameters of the ellipse, is it possible to determine in which of the two foci is the star? To be more precise, if I put into orbit a missile from earth, it will reach first the perihelion and then aphelion or vice versa? How can I know?

You are right, plus the component of gravity mg sin(theta). Being gravity conservative, the real problem is how to calculate the work done by friction. Do you have a solution?

I actually tried that way: - in the radial direction, the law of motion is: N-mgcos(theta)=mv^2/R - in the tangential direction, the only force is friction, that is (mu)m(gcos(theta)+v^2/R). Now, what I find confusing is this: I should integrate to find the work done by friction, but with...

Yes, I should have been more precise.. I meant that the circle is vertical so the normal force along the motion should be mv^2/R+mgcos(theta). Now, I wonder if it is possible to evaluate the work done by friction in this case elementary, so that the final velocity can be easily obtained...

If a body moves along a quarter of a circle and it is subject only to conservative forces, it is relatively easy to deduce the equation of motion. But if friction comes into action, it seems more difficult. Suppose that a body has initial velocity v_0 and that it moves along a quarter of a...