受力前的动量是:Q = mv1 = 10 * 10 = 100kgm/s,受力后的动量是 Q1 = mV2 = 10 * (-2) = -20kgm/s; 物体受到的冲量是 Q‘ = (-20) - 100 = -120kgm/s;
由动量定理得Q’ = Ft 所以F = Q‘ / t = (-120) / 4 = -30N,力F大小为30N,方向跟原运动方向相反
受力前的动量是:Q = mv1 = 10 * 10 = 100kgm/s,受力后的动量是 Q1 = mV2 = 10 * (-2) = -20kgm/s; 物体受到的冲量是 Q‘ = (-20) - 100 = -120kgm/s;
由动量定理得Q’ = Ft 所以F = Q‘ / t = (-120) / 4 = -30N,力F大小为30N,方向跟原运动方向相反