Fr.: masse réduite
The "effective" → inertial mass appearing in the → two-body problem of → Newtonian mechanics. The reduced mass is a quantity which allows the two-body problem to be solved as if it were a one-body problem. For the masses m1 and m2, it is given by the ratio μ = m1m2 / (m1 + m2). The value of μ is generally smaller than m1 and m2. The larger the difference between the two masses, the closer μ will be to the smaller mass. If the particles are of equal mass, μ is half the mass of either.