On the smooth horizontal plane, there is a flat car with a length of 10m and a mass of M = 1kg. There is a small block with a mass of M = 1kg at the left end of the car. The small block is given an initial speed. After a period of time, the block does not fall from the car, and the total speed is 5m / s. The initial speed and dynamic friction factor are calculated

On the smooth horizontal plane, there is a flat car with a length of 10m and a mass of M = 1kg. There is a small block with a mass of M = 1kg at the left end of the car. The small block is given an initial speed. After a period of time, the block does not fall from the car, and the total speed is 5m / s. The initial speed and dynamic friction factor are calculated

According to the conservation of momentum:
MV=(M+m)V’
V=2V’＝10m/s
According to the kinetic energy theorem:
MGUS = 1 / 2mV ^ 2-1 / 2 (M + m) V '＾ 2
1*10*10*u＝1/2*1*10*10-1/2*2*5*5
u＝0.25