Q146 / 180 · AIIMS 2008 · Physics

A bullet is fired from a rifle and the rifle recoils. Kinetic energy of rifle is

  • A
    less than K.E. of bullet
  • Correct answer
    B
    greater than K.E. of bullet
  • C
    equal to K.E. of bullet
  • D
    none of the above

Solution

Momentum of rifle $=$ Momentum of bullet $m_1 v_1=m_2 v_2$, Also $m_1>m_2$ $\begin{aligned} & \frac{\text { K.E. of rifle }}{\text { K.E. of bullet }}=\frac{\frac{1}{2} m_1 v_1^2}{\frac{1}{2} m_2 v_2^2} \\ & =\frac{m_1^2 v_1^2}{m_1} \cdot \frac{m_2}{m_2^2 v_2^2}=\frac{m_2}{m_1}\end{aligned}$ K.E. of rifle is less than K.E. of bullet.

Hence, the correct answer is option: 'B'.

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