Assume: - Mass of incoming particle: \(M = 2m\) - Target mass at rest: \(m\) - Elastic collision: momentum and kinetic energy conserved Use result from elastic collision (scattering in lab frame): If a moving particle of mass \(M\) collides elastically with a stationary particle of mass \(m\), and both particles move after collision, then the angle \(\theta\) between their velocity vectors satisfies: \[ \tan \theta_{\text{max}} = \frac{m}{M} \Rightarrow \tan \theta_{\text{max}} = \frac{m}{2m} = \frac{1}{2} \Rightarrow \theta_{\text{max}} = \tan^{-1} \left( \frac{1}{2} \right) \] Final Answer \[ \boxed{\theta_{\max} = \tan^{-1} \left( \frac{1}{2} \right)} \]

In a scattering experiment, a particle of mass $ 2m $ collides with another particle of mass $ m $, which is initially at rest. Assuming the collision to be perfectly elastic, the maximum angular deviation $ \theta $ of the heavier particle, as shown in the figure, in radians is: 