3. (a) (i) State the parallelogram of forces. (1 mark)
(ii) A metal sphere (Fig. 2) weighing 60 N is suspended from a beam by a thin string. What horizontal force must be applied to the weight to keep the string at an angle of 38° to the vertical? What is the tension in the string? (3 marks)
(b) (i) State the principle of conservation of momentum. (1 mark)
(ii) Two cars of the same mass collide headon and become tangled so that they move on together. If the engines of both were stopped at the moment of impact and the speeds of the cars at impact were 120 m/s and 200 m/s, find the joint velocity immediately after collision. (3 marks)
(b) The semiconductor diode can be used as a rectifier as used in the circuit below? Fig. 5.
(i) What does the term rectification mean? (1 mark)
(ii) The rectification described by the circuit in Fig. 5 above, is half wave rectification. Sketch its waveform which would be seen on a suitably adjusted CRO and explain why the output voltage is so rectified.
(b) The table below gives the results of an experiment to determine the saturation vapour pressure of water at various temperatures. Plot a graph of these results. Use the graph to deduce the:(1½ mark)
(i) vapour pressure of water in a room where the dew point is 8°C. (½ mark)
(ii) boiling point of water at a pressure of 120 mm Hg. (½ mark)