第五题

质心（在距离M的圆心距离mL/(M+m)处)作瞬心
当圆柱体转过δθ角时刚杆转过δΩ=Rδθ/(mL/(M+m))
小球重力提供驱动力mgLΩδΩ=(0.5MR²+MR²)βδθ+βRM(ML/(M+m))δΩ
=> 2(M+m)²g/(ML(2M+3m))=Rβ/θR=a/x
=> 1/T=1/(2π)*√(2(M+m)²g/[ML(2M+3m)])