For example, substituting into m 1 a = m 1 g − − T , results in T = 2 g m 1 m 2 m 1 + m 2 = 2 g 1 / m 1 + 1 / m 2 = m h g where m h = 2 m 1 m 2 m 1 + m 2 is the harmonic mean of the two masses. The numerical value of m h is closer to the smaller of the two masses.