Answer:
40 N
Explanation:
Newton's second law of motion states that the net force acting on the crate is equal to the product between its mass and its acceleration:
[tex]\sum F = ma[/tex]
where
m is the mass
a is the acceleration
In this problem, we have:
- The net force can be written as
[tex]\sum F = F - F_f[/tex]
where
F = 40 N is the horizontal forward push
[tex]F_f[/tex] is the force of friction
Also, we know that the crate moves at constant velocity, so its acceleration is zero:
[tex]a=0[/tex]
By combining all the equations together, we find:
[tex]F-F_f=0\\F_f = F = 40 N[/tex]
So, the force of friction is 40 N.
