(1)mv0=(m+M)V
(2)W1=1/2mv0^2-1/2mv^2;w2=1/2mv0^2-1/2(m+M)V^2-w1
(3)w3=1/2mv0^2-1/2(m+M)v^2
(4)mgulL0=w3
(5)mv0-mv=mgut