m=f0+fem=f_{0}+f_{e}m=f0+fe
m=f0fem=\frac{f_{0}}{f_{e}}m=fef0
m=fef0m=\frac{f_{e}}{f_{0}}m=f0fe
m=v0u0(1+Dfe)m=\frac{v_{0}}{u_{0}}\left(1+\frac{D}{f_{e}}\right)m=u0v0(1+feD)