猴子爬繩(力學問題)

將一滑輪固定於天花板上,並將一繩搭在滑輪上兩繩端垂下.繩之左端掛一石質量M1 =10kg,右端有一翭子質量亦為M2=10kg,緊握繩子靜止懸於半空.問:
1) 猴子向上以加速度 a=3m/s^2爬時,石塊之運動(向上? 向下? a=?)繩之張力T1
2) 猴子向下以加速度 a=3m/s^2爬時,石塊之運動,繩之張力 T2.
1)
T1 - M2 x g = M2 x a
T1 = M2 x (a + g)
Assume g = 10m/s^2,
T1 = 10 x (3 + 10) = 130
繩之張力T1 = 130N
T1 - M1 x g = M1 x a
a = (T1 - M1 x g)/M1
a = (130 - 10x10)/10 = 3
石塊之運動 向上, a=3 m/s^2
2)
T2 - M2 x g = -M2 x a
T2 = M2 x (g - a)
Assume g = 10m/s^2,
T2 = 10 x (10 - 3) = 70
繩之張力T2 = 130N
T2 - M1 x g = M1 x a
a = (T2 - M1 x g)/M1
a = (70 - 10x10)/10 = -3
石塊之運動 向下, a=3 m/s^2