Q 1 :    

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]

  • 40%,2gh

     

  • 50%,gh2

     

  • 50%,2gh

     

  • 50%,gh

     

(C)  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%

 



Q 2 :    

A spherical body of mass 100 g is dropped from a height of 10 m from the ground. After hitting the ground, the body rebounds to a height of 5 m. The impulse of force imparted by the ground to the body is given by (given g=9.8 m/s2)           [2024]

  • 4.32 kg ms-1

     

  • 43.2 kg ms-1

     

  • 23.9 kg ms-1

     

  • 2.39 kg ms-1

     

(4)

m=100g=0.1 kg, h1=10 m, h2=5 m

u=2gh1=2×98 m/s

v=2gh2=98 m/s

Impulse =ΔP=Pf-Pi

=0.1[98+2×98]

2.39 kg m/s



Q 3 :    

A simple pendulum of length 1 m has a wooden bob of mass 1 kg. It is struck by a bullet of mass 10-2 kg moving with a speed of 2×102 ms-1. The bullet gets embedded into the bob. The height to which the bob rises before swinging back is (use g=10 m/s2)         [2024]

  • 0.30 m

     

  • 0.20 m

     

  • 0.35 m

     

  • 0.40 m

     

(2)

Pi=Pfmu=(M+m)V

mu=(M+m)V

10-2×2×1021×VV2 m/s