1. (From 2014 exam) In a physics laboratory, the disc used for a rotational dynamics experiment has fallen off its support and is hanging against the wall as shown in Figure 1. Both the wall and disc have smooth surfaces. The disc has a radius of 25cm and a mass of 3.5 kg. The string holding it has a length of 60 cm and can withstand a maximum tension of 40 N. The string is attached to a small hub at the centre of the disc.
a. Calculate the normal force exerted on the disc by the wall.
b. A student stands below the disc and pulls down on the hub at its centre. With what maximum force can the student pull downwards on the hub before the disc falls on his head?
c. How would your answers to (a) and (b) change if the disc and wall were not very smooth - would they increase, decrease or stay the same? Explain your answers (no calculations required).
2. The two forces F1 and F2 act at point A and give a resultant force of FR= -100N k. Find the magnitude of F2 and its coordinate angles. (Look at the diagram carefully!)
3. The pipe shown is subjected to a force of magnitude F = 800N. Determine the angle θ between F and the pipe segment BA, and the magnitudes of the components of F which are parallel and perpendicular to BA.
