Answer:
The friction force is 250 N
Explanation:
The desk is moving at constant velocity. This means that its acceleration is zero: a = 0. Newton's second law states that the resultant of the forces acting on the desk is equal to the product between mass (m) and acceleration (a):
[tex]\sum F=ma[/tex]
In this case, we know that the acceleration is zero: a = 0, so also the resultant of the forces must be zero:
[tex]\sum F = 0[/tex] (1)
We are only interested in the forces acting along the horizontal direction, since it is the direction of motion. There are two forces acting in this direction:
- the pull, forward, F = 250 N
- the friction force, backward, [tex]F_f[/tex]
Given (1), we have
[tex]F-F_f = 0[/tex]
So the force of friction must be equal to the pull:
[tex]F=F_f = 250 N[/tex]
