Question

A ball is thrown vertically downwards from a height of 20m with initial velocity V it collide with the ground and loses 50% of its energy in the collision and rebounds to the same height the initial velocity V is equal to

Answer 1

Answer: Answer: (C)

Explanation:

Correct option is

C : 20ms  −1

 Initial  energy E  i = PE+KE=mgh+  2/ 1 mv2

 

Energy when it reaches the ground: E=  1/2 mv  ′2  since PE is zero.

Given, E=  1/2   E  i

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Since it rises to the  same height E  f

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=mgh+0 is the final energy

⇒  1/2 (mgh+ 1/2  mv  2 )=E f = mgh+0  v 2 = 2gh=2×10×20=20 power 2

 

⇒v=20m/s

Answer 2

Answer:

20 m/s

Explanation:

see the attached image