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.
5 J -
B.
10 J -
C.
15 J -
D.
20 J
Correct Answer: Option C
Explanation
Height h = 1/2 (U(^2)/g) = 10(^2)/20 = 5m
Energy before hitting ground is = P.E at the height of 5m.
P.E = mgh = 0.1 x 10 x 10= 10 J
K.E = 1/2 MV(^2) = 5J
T.E = K.E + P.E = 5 + 10 = 15J