The mass of the two objects is Ma = 2kg, MB = 4kg, the dynamic friction coefficient between a and B is u = 0.2, and the dynamic friction coefficient between B and the ground is u = 0.4, A. The relative sliding occurs between B and the ground, and the friction between the contact surfaces is calculated

The mass of the two objects is Ma = 2kg, MB = 4kg, the dynamic friction coefficient between a and B is u = 0.2, and the dynamic friction coefficient between B and the ground is u = 0.4, A. The relative sliding occurs between B and the ground, and the friction between the contact surfaces is calculated

Fab=magu(ab)=2*9.8*0.2=3.92N
Fb=(ma+mb)gu(b)=(2+4)*9.8*0.4=23.52N

If Ma = 2kg, MB = 4kg, U1 = 0.2, U2 = 0.4, force F acts on B
When AB moves on the ground at the same speed v = 10m / s, what is the friction between a and B? What is the friction between B and the ground?

The condition of the title is "ab moves in a straight line at a constant speed on the ground at the same speed v = 10m / s", so a moves in a straight line at a constant speed, and the combined external force is 0. Therefore, there is no friction in the horizontal direction. Therefore, the friction between AB is 0
B also moves at a constant speed, so the resultant force of B in the horizontal direction is 0, so the friction force F = f, f = UMG = u (MA + MB) g = 24N