Question

After a totally inelastic collision, two objects of the same mass and same initial speeds are found to move together at half of their initial speeds. The angle between the initial velocities of the objects is :

• A. ${120}^o$
• B. ${60}^o$
• C. ${150}^o$
• D. ${45}^o$

Answer 1

The correct option is A ${120}^o$

Along X-direction--

Initial momentum $=P_1=2mv\cos \theta$

Final momentum $=P_2=\left(2m\right)V=2m\times \frac{v}{2}=mv$

From Conservation of Momentum along X-direction-

$2mv\cos \theta =mv$

$⟹\cos \theta =\frac{1}{2}$

$⟹\theta ={60}^o$

Angle between the velocities of two masses before collision $=2\theta ={120}^o$

Answer-(A)