Answer
(a) A minimum force of 15.78 N is required to make the block start to slide.
(b) Since the net force is non-zero, the block accelerates.
(c) $a = 1.27~m/s^2$
Work Step by Step
(a) In order to make the block start moving, the minimum force $F$ required is equal in magnitude to the maximum possible value of the static friction force:
$F = mg~\mu_s$
$F = (4.6~kg)(9.80~m/s^2)(0.35)$
$F = 15.78~N$
A minimum force of 15.78 N is required to make the block start to slide.
(b) We can calculate the net force when the block is sliding:
$\sum F = F-mg~\mu_k$
$\sum F = 15.78~N-(4.6~kg)(9.80~m/s^2)(0.22)$
$\sum F = 5.86~N$
Since the net force is non-zero, the block accelerates.
(c) We can find the acceleration:
$ma = \sum F$
$a = \frac{\sum F}{m}$
$a = \frac{5.86~N}{4.6~kg}$
$a = 1.27~m/s^2$
