A ball of mass 0.1kg is thrown vertically upwards with a speed of 10ms‾¹ from the top of a tower 10m high. Neglecting air resistance, its total energy just before hitting the ground is? (Take g = 10ms‾²)

A. 5J
B. 10J
C. 15J
D. 20J

Correct Answer:

Option C = 15J

Explanation
Given
m = 0.1kg
u = 10ms⁻¹
h = 10m
g = 10ms⁻²
At h_max; v = 0

Using
v̸ = u̸ = g̸t
/0 = w̸ – /10t
v² = u² – 2gh
0² = 10² – 2 x 10h
20h = 100
h = 5m
Total height = 10 + 5
= 15m
Total energy = mghr = 0.1 x 10 x1 5
= 15J