1) We know, W = F s
w = 30 15
w = 450 Joules
Now, Power = work done / Time taken
p = 450 / 8
p = 56.25 Watts
2) When ball lifts from bottom to the top, it's P.E. will rise to the top and it will be greatest at the top point, whereas K.E. will decrease during the rise, and it will be lowest at the highest point, and will be maximum at the bottom point, when potential energy will be zero
3) On the Top, you have highest potential energy as it is directly proportional to the height of the object/person, and for bottom, it will be zero whereas Kinetic Energy will be maximum as sum of their magnitude must be constant at each instances (According to Law of Conservation of Energy).
Friction will decrease the amount of Energy by some extent due to it's opposing nature
4) Potential Energy (Initial one) = m g h
= 25 9.8 4 = 980 J
Kinetic Energy = 1/2 mv²
= 1/2 25 5² = 312.5 J
Energy lost = Final - Initial = 980 - 312.5 = 667.5 Joules
Hope this helps!
