Question

A horizontal 20.-newton force is applied to a 5.0-kilogram box to push it across a rough, horizontal floor at a constant velocity of 3.0 meters per second to the right. What is the coefficient of kinetic friction between the box and the floor?

Answer 1

`mu` = `0.4`

Explanation:

When a body moves with constant velocity on a rough surface due to application of a certain amount of force,it means that this amount of force was enough to just overcome the frictional force acting along the surface of contact i.e no net force is acting on it.

So, we can say,
`F = f` (where `F` is the force applied for moving the box and `f` is the frictional force acting on it)

So, `20`= `mu*N` = `mu*m*g`(N is normal reaction and `mu` is the kinetic frictional coefficient)
So, `20` = `mu*5*10`
Or, `mu` = `0.4`