Question

The diagram below represents a horizontal force of 20 newtons applied to a 5.0 kilogram box to push it and

rough, horizontal floor at a constant velocity of 3.0 m/s to the right.
3.0 m/s
20 N
5.0 kg
B. Determine the magnitude of the force of friction acting on the box. Explain your answer.

Answer 1

20 N

Step-by-step explanation:

There are two forces acting on the box:

- The force of push, F, forward, of magnitude F = 20 N

- The force of friction,
`F_f`, backward

So, the equation of motion for the box is

`F-F_f = ma`

where

m = 5.0 kg is the mass of the box

a is its acceleration

The box is sliding at constant velocity: this means that its acceleration is zero

a = 0

So, the equation becomes

`F-F_f = 0`

Therefore, we can find the magnitude of the force of friction:

`F_f = F =  20 N`