Question 2

A man faces difficulty while swimming in a dam. During the rescue operation, an inflated tube attached to a helicopter by a rope is dropped from the helicopter.
The man, of mass 70 kg, holds onto the inflated tube of mass 4 kg, while the helicopter is flying horizontally at a CONSTANT speed. An average frictional force of 300 N is exerted on the man-tube combination while they are dragged horizontally along the surface of the water by the helicopter. The rope makes an angle of 50° with the surface of the water, as shown in the diagram below.
Assume that the rope is inextensible and massless, and the water of the dam does not
flow.

2.1 State Newton’s First Law of Motion in words. (2)

2.2 Draw a free-body diagram of the man-tube combination while they are being dragged. (4)
2.3 Calculate the tension in the rope. (4)

2.4 How will the answer to QUESTION 2.3 change if the helicopter ACCELERATES while dragging the man? The frictional force and the angle between the rope and the surface of the water remain the same.
Choose from INCREASES, DECREASES or NO CHANGE. Give a reason for the answer. (2)

In another rescue operation, the inflated tube of mass 4 kg is dropped from the
stationary helicopter and it strikes the water at a speed of 16 m∙s^-1. The tube sinks vertically downwards into the water to a depth of 0,8 m and then rises to the surface.
The rope hangs loosely.

2.5 Calculate the magnitude of the average upward force exerted on the inflated tube while it is sinking. Assume that the average upward force is constant for the motion. (5)
[17]