Answer:
a). whenever the ball is at it's highest on either side (it stops, so kinetic energy is 0)
b). whenever the ball is at the bottom (A) - it cannot go lower, so potential energy is 0.
c). whenever the ball accelerates, so when it's going down from either side before reaching A (at that point it's going up and thus slowing down).
d). whenever the ball is ascending, so when it's goind up from A to either side
Explanation:
Kinetic energy is based on velocity
[tex]E_K = \frac{mv^2}{2}[/tex]
mass is constant, so we need to find a point where v = 0 to solve a), and points where v is increasing to solve b).
Potential energy is based on height vs "the bottom" (here, the minimum altitude is "the bottom").
[tex]E_P = mgh[/tex]
mass and gravitational acceleration are constant, so we need to find a point where h = 0 to solve b) and the points where h is increasing to solve d).
