# 2 hard angular momentum problems

## Homework Statement

the easier one
Atwood's Machine. The masses are M and 2M, and the pulley is a uniform disk of mass M and radius R. the string is massless and does not slip with respect to the pulley. Find the acceleration of the masses. Use force and Torque.
answer should be something like a=2g/7 (using conservation of energy) but i only care about how to get there using force and torque

The harder one
A coin stands vertically on a table. It is projected forward (in the plane if itself) with speed V and angular speed w. The coefficient of kinetic friction between the coin and the table is u. What should V and w be so that the coin comes to a rest(both translationally and rotationally) a distance d from where it started.
the coin in this problem has a backward spin. it is not rolling forward.

I know the general equations here I am really just looking for a prob in the right direction. I really do not know how to approach these questions.

L=rxp
t=dL/dt
t=rxF
dL/dt=d/dt(rxp)