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Laws Of Motion

Question
CBSEENPH11026342

A ball of mass m hits the floor with a speed v making an angle of incidence θ with the normal. The coefficient of restitution is e. The speed of reflected ball and the angle of reflection of the ball will be

     

  • v' = v, θ = θ'

  • v' = v2, θ = 2θ'

  • v' = 2v, θ = 2θ'

  • v' = 3v2, θ = 2θ'3

Solution

A.

v' = v, θ = θ'

The coefficient of restitution is a number which indicates how much kinetic energy ( energy of motion ) remains after collision of two object.

The parallel component of velocity of the ball remains unchanged. This gives

           v' sinθ = v sinθ                   .... (i)

For the components normal to the floor, the velocity of separation = v' cosθ

Hence  v' cosθ' = e v cosθ               .....(ii)

From equations (i) and (ii)

            v' = sin2θ + e2 cos2θ

and       tanθ' = tanθe

For elastic collision, e = 1, so that 

          θ' = θ  and  v' = v