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GHS S.3 PHYSICS HOLIDAY WORK MAY/JUNE 2016 1. (a) (i) Define pressure. (ii) Explain briefly why a needle enters deeper into the human fresh than a nail even when the same force is applied on each. (b) (i) With the aid of a labeled diagram describe the action of a force pump. (ii) In a force pump, a force of 50N is applied on a piston of diameter 0.4m during the down stroke. Find the pressure exerted on the water by the piston. (c) (i) Define moment of a force. (ii) State two ways of increasing the stability of an object. (d) (i) A uniform metre rule of mass 80g is pivoted at the 30cm mark. Find the mass that would be placed at the 5cm mark for the metre rule to be in equilibrium. 2. (a) what is meant by: (i) Velocity ratio of a machine? (ii) Pitch of a screw? (b) A screw jack with a lever arm of 40cm and a pitch 2.0cm is used to raise a heavy load . (i) Find the velocity ratio of the screw jack (ii) State two practical applications of block and tackle pulley system 3. (a)State Ohm’s law 3.6Ω 4Ω 6Ω A battery of e.m.f 6Vand negligible interval resistance is connected to 3.6Ω, 4Ω and 6Ω resistors as a shown in figure 1 above. Find the: (i) Total current flowing through the circuit. (ii) Power dissipated in the 3.6Ω resistor (b) Sketch the I – V characteristics for the filament of a lamp. 4.(a) (i) Define pressure. (ii) Describe a simple experiment to show that pressure in a liquid increases with depth. (b) Figure below shows a hydraulic press. A and B are cylindrical pistons of radii 2cm and 0.4m respectively. A B Calculate the maximum load at B that can be overcome by a force of 78N applied at A. (c) (i) Draw a diagram of a pulley system having a velocity of 5. (d) In the gear system in figure 2 below, N1 and N2 are the number of teeth on the wheels. The efficiency of the gear system is 60%. N2 = 100 N1 = 20 Find; 5. (a) (i) the velocity ratio. (ii) the load that can be raised by an effort of 200N. (e) Explain why a longer ladder is preferred to a shorter ladder when climbing a tree. What is meant by the following terms as applied to waves. (i) Amplitude (ii) Period (iii) (b) State the factors that affect the frequency of vibrating string. (c) Describe an experiment to show reflection of sound waves. (d) (i) Describe how echo sounding is used to determine the depth of the sea. (ii) A long open tube is partially immersed in water and a turning fork of frequency 425HZ is sounded and held above it. If the tube is gradually raised. Find the length of the air column when the resonance first occurs. END.