Q.

If a rubber ball falls from a height h and rebounds up to the height of h/2. The percentage loss of total energy of the initial system as well as velocity ball before it strikes the ground, respectively, are                 [2024]

1 40%,2gh  
2 50%,gh2  
3 50%,2gh  
4 50%,gh  

Ans.

(3)  

       Velocity just before collision = 2gh

        Velocity just after collision = 2g(h2)

        ∴     ∆KE=12m(2gh)-12mgh=12mgh

        ∴     % loss in energy ∆KEKEi×100

         ⇒∆KEKEi×100=12mgh12mg2h×100=50%