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: C
Explanation
Givn m = 0.1kg u = 10ms\(^{-1}\) h = 10m g = 10ms\(^{-2}\) At h\(_{max}\); v = 0 Using \(\not v\) = \(\not u\) = \(\not gt\) \(\not 0\) = \(\not w\) - \(\not 10t\) v\(^{2}\) = u\(^{2}\) - 2gh 0\(^{2}\) = 10\(^{2}\) - 2 x 10h 20h = 100 h = 5m Total height = 10 + 5 = 15m Total energy = mghr = 0.1 x 10 x1 5 = 15J
