A stationary particle breaks into two parts of masses $m_A$ and $m_B$ which move with velocities $v_A$ and…

A stationary particle breaks into two parts of masses $m_A$ and $m_B$ which move with velocities $v_A$ and $v_B$ respectively. The ratio of their kinetic energies $\left(K_B: K_A\right)$ is :
  1. $v_B: v_A$
  2. $m_B: m_A$
  3. $m_B v_B: m_A v_A$
  4. $1: 1$

Solution

Initial momentum is zero. $\begin{aligned} & \text { Hence }\left|\mathrm{P}_{\mathrm{A}}\right|=\left|\mathrm{P}_{\mathrm{B}}\right| \\ & \Rightarrow \mathrm{m}_{\mathrm{A}} \mathrm{v}_{\mathrm{B}}=\mathrm{m}_{\mathrm{B}} \mathrm{v}_{\mathrm{B}} \\ & \frac{(\mathrm{KE})_{\mathrm{A}}}{(\mathrm{KE})_{\mathrm{B}}}=\frac{\frac{1}{2} \mathrm{~m}_{\mathrm{A}} \mathrm{v}_{\mathrm{A}}^2}{\frac{1}{2} \mathrm{~m}_{\mathrm{B}} \mathrm{v}_{\mathrm{B}}^2}=\frac{\mathrm{v}_{\mathrm{A}}}{\mathrm{v}_{\mathrm{B}}} \\ & \frac{(\mathrm{KE})_{\mathrm{B}}}{(\mathrm{KE})_{\mathrm{A}}}=\frac{\mathrm{v}_{\mathrm{B}}}{\mathrm{v}_{\mathrm{A}}}\end{aligned}$

Asked in: JEE Main 2024 (08 Apr Shift 1)

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