The diagram in the figure below represents a wheel and axle used as a machine, whose efficiency is 80% to raise 400N of building materials. The wheel and axles have diameters of 75cm and 15cm respectively.

​(a) The diagram in the figure below represents a wheel and axle used as a machine, whose efficiency is 80% to raise 400N of building materials. The wheel and axles have diameters of 75cm and 15cm respectively.

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The diagram in the figure below represents a wheel and axle used as a machine, whose efficiency is 80% to raise 400N of building materials. The wheel and axles have diameters of 75cm and 15cm respectively.

​(i) Mark on the diagram the correct position and direction of the load to be lifted (1mk)

​(ii) Name the principle on which this machine works (1mk)

​The principle of moments

​(iii) Calculate the effort needed to raise the load (3mks)

​(iv) The machine is operated manually and raises the load to a height of 5m in 20 seconds. Calculate the power developed by the operator (2mks)

(b)
​(i) State two factors that determines the efficiency of an inclined plane as a machine (2mks)

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1. ​Smoothness of plane
2. angle of inclination

​(ii) Explain how these factors affect efficiency (2mks)

• Smoothness: Efficiency increases with smoothness since loses due to friction and minimized
• Angle –efficiency increases with the angle of inclination since normal reaction decreases and so does friction.