a box is being pushed at a constant velocity. The coefficient of kinetic friction between the box and the surface is 0.3 . At one point in the journey the coefficient of kinetic friction between the box and the surface suddenly jumps to 0.55. if the force of the push does not change, what is the acceleration of the box after change in friction?

1 answer

At the beginning, the box is in uniform rectilinear motion (URM), which means that the horizontal force is just enough to balance the frictional resistance, where
Pushing force, F
=Frictional resistance = μkmg
= 0.3 mg

With increase in coefficient of friction,
the net force on the box is now
F=(0.3-0.5)mg=-0.2mg
Acceleration = F/m=-0.2g
i.e. decelerting