A ball is thrown vertically downward with a velocity of 20 m/s from the top of a tower. It hits the ground after some time with a velocity of 80 m/s. The height of the tower is : (g = 10 m/s2)
- 340 m
- 320 m
- 300 m
- 360 m
Answer
(3) 300 m
Solution
Taking the downward direction as positive, u = 20 m/s, v = 80 m/s and a = g = 10 m/s2. Using v2 = u2 + 2gh,
802 = 202 + 2 10 h
6400 - 400 = 20h
h = 600020 = 300 m
Answer: (3)