Q193 / 200 · Manipal (MET) 2012 · Physics

Two bodies of different masses $m_1$ and $m_2$ have equal momenta. Their kinetic energies $E_1$ and $E_2$ are in the ratio

  • A
    $\sqrt{m}_1: \sqrt{m}_2$
  • B
    $m_1: m_2$
  • Correct answer
    C
    $m_2: m_1$
  • D
    $m_1^2: m_2^2$

Solution

Given - Momentum of two bodies are same i.e. $p_1=p_2$ and mass of two bodies $m_1$ and $m_2$ The relationship between the kinetic energy (KE) and Linear momentum ( p ) is - Momentum of first body whose mass is $\mathrm{m}_1$. $p=\sqrt{2 m_1 K E_1}$ $\qquad ...\mathrm{(1)}$ Momentum of second body whose mass is $\mathrm{m}_2$ $p=\sqrt{2 m_2 K E_2}$ $\qquad ...\mathrm{(2)}$ Divide equation (1) and (2). $\begin{aligned} & \frac{p}{p}=\frac{\sqrt{2 m_1 K E_1}}{\sqrt{2 m_2 K E_2}} \\ & \sqrt{2 m_2 K E_2}=\sqrt{2 m_1 K E_1} \end{aligned}$ By squaring both side, we get $\begin{aligned} & 2 m_2 K E_2=2 m_1 K E_1 \\ & \frac{K E_1}{K E_2}=\frac{m_2}{m_1} \end{aligned}$

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

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