Question

The coefficient of kinetic friction between a refrigerator (mass 107 kg) and the floor is 0.18, and the coefficient of static friction is 0.88. After struggling to move the refrigerator, you finally apply enough force to get it moving. What is the minimum force required to keep it moving with a constant velocity?

Answer 1

Here we are going to find out the enough required force to get it moving with a constant velocity, it means,Suppose you push the refrigerator horizontally with enough force to make the refrigerator start to move, and you continue to apply the same amount of force even after it starts moving.

In this case, one has to overcome the force of static friction for the refrigerator to move (F = µs m g).

F = µs m g = 0.88 x 107 Kgx 9.8 m/s² = 922.768 N

Note: The force due to static friction is the least amount of force applied to the refrigerator for its motion.

If we maintain the same force then one has to overcome the force due to kinetic friction for the refrigerator to be in motion (Fk = −µk m g).

Fk = −µk m g = -0.18 x 107 Kgx 9.8 m/s² = -188.748 N

The net force is F + Fk = 922.768 N + (-188.748) = 734 N --------Ans

Note : The friction force is directed opposite to the motion of the object.