30.) x0 = displacement of m
let amplitude of M=x
m(x0-x) - Mx = 0 = com at rest initially
=> x = mx0/(m+M) ----------> amplitude of M
amplitude of m = Mx0/(m+M)
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now vel of m= Mv0/(m+M)
vel of M= mv0/(m+M)
extension in spring = x0
now... by energy method..
U= 1/2M[mv0/(m+M)]2 + 1/2m[ Mv0/(m+M)]2 + 1/2kx02
now differentiate and do al the traditional works ;)
then u will get
T= 2pi√μ/k
where μ=mM/M+m