If an object is moving with a constant velocity, then the net force acting on it is zero. This means that the force of kinetic friction is equal in magnitude to the force applied to the object. Therefore, we can easily determine the coefficient of kinetic friction by dividing the force of kinetic friction by the normal force.

$$\mu_k = \frac{F_k}{F_n}$$

Where:

- \(\mu_k\) is the coefficient of kinetic friction

- \(F_k\) is the force of kinetic friction

- \(F_n\) is the normal force

If the object is not moving with a constant velocity, then the net force acting on it is not zero and the force of kinetic friction is not equal in magnitude to the force applied to the object. This makes it more difficult to determine the coefficient of kinetic friction.