A rubber ball is dropped from a height of 5m on a plane,

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A rubber ball is dropped from a height of 5m on a plane, where the acceleration due to gravity is not shown. On bouncing it rises to 1.8 m. The ball loses its velocity on bouncing by a factor of

1. 16
  25
2. 2
  5
3. 3
  5
4. 9
  25

Correct Option: B

According to principle of conservation of energy
Loss in potential energy = Gain in kinetic energy

⇒ mgh =	1	mv² ⇒ v = √2gh
	2

If h₁ and h₂ are initial and final heights, then
v₁ = √2gh₁ , v₂ = √2gh₂
Loss in velocity , ∆v = v₁ - v₂ = √2gh₁ - √2gh₂
∴ Fractional loss in velocity

= 1 - √0.36 = 1 - 0.6 = 0.4 =	2
	5