Two blocks A(2 kg) and B(5 kg) rest one over the other on a smooth horizontal plane. The coefficient of static and dynamic friction between A and B is the same and is equal to 0.60. The maximum horizontal force that can be applied to B in order that both A and B do not have relative motion is   TAKE g= 10 ms-2

Let due to a force F on B, both blocks A and B, both blocks A and B move together. In this case,F=mA+mBa=(2+5)a∴ a=(F/7)Now force on A=m a=2×(F/7)For no relative motion between A and B, (2F / 7) must not exceed the limiting force of friction between, A and B. The limiting force of friction between A and B is given byμmAg=0⋅6×2×g∴ 2F7=0⋅6×2×gF=4⋅2N g=4⋅2kgf.