Question

A ball is thrown vertically downwards from a height of 20 m with an initial velocity υ0​. It collides with the ground, loses 50 percent of its energy in collision and rebounds to the same height. The initial velocity υ0​ is

Answer 1

Explanation:

Initial energy E

i

=PE+KE=mgh+

2

1

mv

2

Energy when it reaches the ground: E=

2

1

mv

′2

since PE is zero.

Given, E=

2

1

E

i

Since it rises to the same height E

f

=mgh+0 is the final energy

⇒

2

1

(mgh+

2

1

mv

2

)=E

f

=mgh+0

v

2

=2gh=2×10×20=20

2

⇒v=20m/s