Answer:
(a)10.5 rad/s2
(b) 20.9 rev
(c) 47.27 m
Explanation:
As the block of mass 53 kg is falling and pulling on the rope. The tension force on the rope must be equal to the gravity acting on the block according to Newton's 3rd law
T = mg = 53*9.81 = 519.93 N
Since this tension force would rotate the cylinder freely without any friction. The torque created by this tension force is
To = TR = 519.93 * 0.36 = 187.17 Nm
This solid cylinder would have a moment of inertia around it's rotating axis of:

(a)We can use Newton's 2nd law to calculate the angular acceleration exerted by such torque on the solid cylinder

(b) With such constant angular acceleration, the angle it would make after 5s is

Since each revolution equals to
of angle, we can calculate the number of revolution it makes

(c) Assume the thickness of the rope is negligible (and its wounded radius is unchanging), we can calculate the rope length unwinded after rotating 131.3rad

Refer to the diagram shown below.
The net force acting on the box is 17 - 13 = 4 N to the right.
The box moves on a friction surface by 3.5 m to the right.
By definition,
Work = Force x Distance.
(a) The work done by the girl is
W₁ = (17 N)*(3.5 m) = 59.5 J
(b) The work done by the boy is
W₂ = (13 N)*(-3.5 m) = - 45.5 J
(c) The work done by the net force is
W₃ = (4 N)*(3.5 m) = 14 J
Note that W₃ = W₁ + W₂
Answers:
(a) 59.5 J
(b) - 45.5 J
(c) 14 J