Question

A ball kept at 20 m height falls freely in downward direction vertically and hits the ground. The coefficient of restitution is 0.4. After the first rebound, the upward velocity is g = 10 m/s² ?

Options

• 4 m/s

• 8 m/s

• 16 m/s

• 12 m/s

Answer 1

8 m/s

Explanation:

h = 20 m, e = 0.4 m

∴ v² = 0 + 2gh = 2 × 10 × 20

∴ v = 2 × 10 = 20

`e="u"/"v"`

∴ u = ev = 0.4 x 20 = 8 m/s