Explanation:
(a) As it is given that there is no vertical displacement. Hence, the forces on y-axis are equal and opposite.
Also, it is known that F = mg
So, F = [tex]56 kg \times 9.8 m/s^{2}[/tex]
= 548.8 N
Also, [tex]F_{f} = \mu N[/tex]
where, [tex]\mu[/tex] = coefficient of kinetic friction
N = force calculated
Putting the values into the formula as follows.
[tex]F_{f} = \mu N[/tex]
= [tex]0.21 \times 548.8[/tex]
= 115.25 N
Hence, the magnitude of the frictional force is 115.25 N.
(b) Now, let us assume that the acceleration is towards the positive x-direction.
[tex]F - F_{f} = ma[/tex]
[tex]548.8 N - 115.25 = 56 \times a[/tex]
a = 7.74 [tex]m/s^{2}[/tex]
Therefore, the magnitude of the crate's acceleration is 7.74 [tex]m/s^{2}[/tex].
