A) The formula for kinetic energy is E = 1/2 mv^2, so the energy of the ball is 1/2 * 2 * 10^2 = 100J.
b) Energy is always conserved, and so if no energy is lost to resistive forces then all 100J of kinetic energy came from its potential energy at the top of the track.
c) The formula for potential energy is E = mgh, which we can rearrange for h = E/mg. We know the energy, the mass and the strength of gravity, so we can find h = 100 / (2*9.81) = 5.10m.
Car X traveled 3d distance in t time. Car Y traveled 2d distance in t time. Therefore, the speed of car X, is 3d/t, the speed of car Y, is 2d/t. Since speed is the distance taken in a given time.
In figure-2, they are at the same place, we are asked to find car Y's position when car X is at line-A. We can calculate the time car X needs to travel to there. Let's say that car X reaches line-A in t' time.

Okay, it takes t time for car X to reach line-A. Let's see how far does car Y goes.

We found that car Y travels 2d distance. So, when car X reaches line-A, car Y is just a d distance behind car X.
I believe you use 4? I’m really unsure about that but I like your Joy Division picture
M=meter, km=kilometer, mm=millimeter, mg=micrometer, cm=centimeter
Answer:

Explanation:
Since there is no friction angular momentum is conserved. The formula for angular momentum thet will be useful in this case is
. If we call 1 the situation when the student is at the rim and 2 the situation when the student is at
from the center, then we have:

Or:

And we want to calculate:

The total moment of inertia will be the sum of the moment of intertia of the disk of mass
and radius
, which is
, and the moment of intertia of the student of mass
at position
(which will be
or
) will be
, so we will have:

or:

which for our values is:
