A ball moving with a velocity `v` hits a massive wall moving towards the ball with a velocity a. An elastic impact lasts for time `/_\t`

Options

A. b, c
B. a, d
C. b, d
D. c, d

Answer

A

Explanation

Velocity of ball after collision is
`V_("bal")~=-(v+2u)and v_("wall")~=u`
Since, `F_("ball")=((Deltap)/(Deltat))_("ball")=(-m(v+2u)-mv)/(Deltat)`
`rArr" "F_("ball")=(-2m(v+u))/(Deltat)rArr|F_("ball")|=(2m(v+u))/(Deltat)`
Increase in K.E. of ball is given by
`DeltaK=(1)/(2)m(v+2u)^(2)-(1)/(2)mv^(2), DeltaK=2 m u(u+v)`