This question tested candidates understanding on the concept of conservation of energy. Majority of the candidates were able to solve this problem. However, few candidates could not solve this question correctly because they lack the knowledge that at maximum height the potential energy P.E is equal to the kinetic energy K.E
The expected answer is:
At max. Ht, P.E = initial K.E
= ½ mu2
= ½ x 0.5 x (25)2
= 156.25 J
OR
V2 = u2 - 2gh
At maximum height, v = 0
O = 252 - 2 x 10h
h = 31.25m
P.E = mgh
= 0.5 x 10 x 31.25
= 156.25J