Answer:
T = 480.2N
Explanation:
In order to find the required force, you take into account that the sum of forces must be equal to zero if the object has a constant speed.
The forces on the boxes are:
(1)
T: tension of the rope
M: mass of the boxes 0= 49kg
g: gravitational acceleration = 9.8m/s^2
The pulley is frictionless, then, you can assume that the tension of the rope T, is equal to the force that the woman makes.
By using the equation (1) you obtain:

The woman needs to pull the rope at 480.2N
Answer:
Part a)

Part b)

Part c)

Explanation:
Part a)
As we know that there is no external torque on the system of two twins
so here we will use



Part b)
Since angular momentum is conserved here as there is no external torque
so we will have



Part c)
Work done by both of them = change in kinetic energy
so we have




Answer:
a) 0 m/s
b) 4 m/s
Explanation:
The average velocity would end up being 0 because it is displacement over time and the displacement here is 0. However, speed is total distance over time which here is 400/100 so it is 4.