A 5 kg block is pushed by a constant horizontal force.The block has an initial velocity of 6 m/s in the direction of the force and it slides on a frictional surface with a coefficient of kinetic friction of 0.25a.what is the magnitude of the horizontal force necessary to keep the block moving at 6 m/s?b.Calculate the force that will increase the kinetic energy of the block by 30J in 2 metersc.calculate the acceleration from the force calculated in part b 英语
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【答案】 a, 由于初速度是6m/s,要保持这个速度,推力要等于摩擦力
Friction force: F = M*G*f = 5*10*0.25 = 72.5(N)
b, 推力除克服摩擦力外,还做功：
E = (F1 - F )*2 = 30;
F1 = 15+72.5 = 87.5 (N)
c, F1 = M*a ;
a = F1/M = 87.5/5 = 17.5 (m/s^2)