There is a piece of wood on the horizontal ground with mass m, and the coefficient of sliding friction between it and the ground is μ. Under the action of the horizontal constant force F, the object starts to move from rest. After time t, the force F is removed, and the object moves forward for time 2T before it stops______ ．

There is a piece of wood on the horizontal ground with mass m, and the coefficient of sliding friction between it and the ground is μ. Under the action of the horizontal constant force F, the object starts to move from rest. After time t, the force F is removed, and the object moves forward for time 2T before it stops______ ．

The acceleration under the action of F is: A1 = f − μ MGM = FM − μ g, the acceleration after removing f is: A2 = μ MGM = μ g, according to v = at, because the ratio of acceleration time and deceleration time is 1:2, the acceleration of uniform acceleration and uniform deceleration is 2:1, so FM − μ g = 2 μ g, the solution is: F = 3 μ mg. So the answer is: 3 μ mg