# Formula Reduced mass of a two-body system

## Reduced mass

`\( \mu \)`Unit

`\( \mathrm{kg} \)`

Effective mass is used to reduce a two-body problem (e.g., the motion of the Earth around the Sun about the common center of mass) to a one-body problem.

If \( m_1 ~\gg~ m_2 \) holds, then the formula for the reduced mass can be approximated by the mass of the lighter body: \( \mu ~\approx~ m_2 \).

## Mass

`\( m_1 \)`Unit

`\( \mathrm{kg} \)`

This can be for example the mass of the earth moving around a center of mass C.M. of the earth and sun.

## Mass

`\( m_2 \)`Unit

`\( \mathrm{kg} \)`

This can be, for example, the mass of the Sun rotating around a center of mass of the Earth-Sun system.