How many head-on, eleastic coillisions must a neutron have with deuterium nucleus to reduce its energy from `1 MeV` to `0.025 eV`.

Explanation

To solve the problem of how many head-on elastic collisions a neutron must have with a deuterium nucleus to reduce its energy from 1 MeV to 0.025 eV, we can follow these steps:

### Step 1: Understand the Energy Loss in a Collision
In a head-on elastic collision between two particles, the energy lost by the neutron can be expressed as:
\[ \Delta E = \frac{4 m_1 m_2}{(m_1 + m_2)^2} E_0 \]
where:
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