A particle of mass `m` strikes another particle of same at rest. Find the angle between velocities of particles after the collision , if the collision is elastic.

Explanation

To solve the problem of finding the angle between the velocities of two particles after an elastic collision, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Problem**:
- We have two particles, each with mass \( m \). One particle is moving with an initial velocity \( v \) and strikes the second particle, which is at rest.

2. **Conservation of Momentum**:
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