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 answerC$m_2: m_1$
- 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'.