When a 1kg mass is dropped from the top of a building 20m high it hits the Earth with a speed of 20m/s. What would be its speed if the same experiment was carried out on a planet where the acceleration due to gravity is ¼ that on Earth?

Answer:

22) D

Acceleration on Earth = 10 m/s²
¼ of Earth’s acceleration = 2.5 m/s²

u = 0
a = 2.5
s = 20
v = ?

v² – u² = 2as

Since u = 0,
v² = 2 (2.5) (20)

v² = 5 x 20 = 100

v = 10 m/s²