Find the velocity at which the relativistic momentum of a particle exceeds its Newtonian momentum `eta=2` times.

Explanation

To find the velocity at which the relativistic momentum of a particle exceeds its Newtonian momentum by a factor of 2, we can follow these steps:

### Step 1: Define Newtonian and Relativistic Momentum
The Newtonian momentum \( p_N \) of a particle is given by:
\[ p_N = m_0 v \]
where \( m_0 \) is the rest mass of the particle and \( v \) is its velocity.
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