# Working out kinetic energy and speed

Tags:
1. Nov 10, 2015

### Meezus

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

a) I think I just have to work out the potential energy and the maximum kinetic energy would is the same?

c) Once I've found the kinetic energy, I'm able to work out velocity. Would the velocity be the maximum speed?

c) I think I can take the PE from A and the PE C and take them away from each other. With this number I'd have the KE of C which i'd work out velocity with?

2. Nov 10, 2015

### JBA

Your approach is correct. Thus problem is a simple matter of the exchange of energy between PE and KE.

3. Nov 10, 2015

### haruspex

To be accurate...
Since there's no friction, the loss in PE equals the gain in KE. So the maximum loss in PE equals the maximum gain in KE.
PE is a relative thing. You cannot say exactly what the PE is at some point unless you have defined some reference value, such as the PE at another point.
No, velocity is a vector. Given the KE and the mass you can deduce the magnitude of the velocity (i.e. its speed) but not the direction.