Work Energy Power – Worksheet problem solution (Q4)
A 1 kg ball is thrown up with a speed of 19.9 m/s. Calculate the work done by its weight in one second.
The height travelled by the ball in 1 sec =h = ut – (1/2) g t2 = (19.9)(1) – (1/2) (9.8) (1)2 = 15 m
Here we have to find out the work done by the weight of the ball. The weight of the ball is = 1×9.8 N = 9.8 N acting downwards.
So the angle between the force and displacement is 180 degrees here.
So work done = Fd cos θ = 9.8 x 15 x cos 180 = – 147 Joule.