1. SIMPLE MACHINES Is a device use to make work easier In a machine,force applied at one point produces a force at another point in order to overcome a load

2. Examples of simple machines 1)Lever 2)Pulleys 3)Pulley belts 4)Gears 5)Hydraulic press 6)Screw 7)Inclined planes 8)The wheel and axle 3. Terms used in the study of machines Effort Force applied on the machine Load Force exerted by the machine NB: The SI unit of effort and load is Newton(N) 4. Mechanical Advantage (M.A) The ratio of load to effort Mathematically, M.A is a ratio of two units hence it has no unit M.A depends on: 1)Friction between the moving parts of the machine 2)The weight of the parts of the machine that have to lifted when operating it. Therefore, M.A cannot be 100% M . A= Load Effort 5. Velocity Ratio (V.R) The ratio of effort distance to load distance Mathematically, V.R is a ratio of two distances hence it has no unit NB: If two machines have velocity ratios VR1 and VR2 then, the resultant VR is given by; VR = VR1 x VR2 V . R .= Effort distance Load distance 6. Efficiency (E) The ratio of work output to work input E is always expressed as a percentage Mathematically, Work output is the work done on the load Work input is the work done by the effort Therefore, E= Work output Work input 100 0 0 E= Work doneon the load Work done by the effort 100 0 0 E= LoadLoad distance EffortEffort distance 100 0 0 7. Efficiency (E) E=( Load Effort )( Load distance Effort distance )100 0 0 E= M . A V . R 100 0 0 8. Efficiency (E) E of a machine is always less than 100% because some energy is lost in overcoming the friction force and the weight of the parts that have to be lifted 9. Quiz In a machine, an effort of 20N is applied to move a load of 80N through a distance of 2cm. Given that effort moves through 0.5m, determine: (a)MA (b)VR (c)E 10. levers They work on the principle of moments Effort arm Load Load arm V .R= Effort arm Load arm 11. The inclined plane Can be used to ease the loading of a heavy luggage on the back of a lorry. The load is moved thro' h by an effort which covers a distance x L h E 0 x V .R= Effortdistance(x) Loaddistance(h) = x xsin0 = 1 sin0 sin0= h x h=xsin0 12. In this case; Work output/work done on the load is given by; Work input/work done by the effort is given by; Workoutput=Loaddistance=mgh Workinput=Effortdistance=Ex= Eh sin0 13. Quiz In the previous figure, take L=50kg, h=4m, =30 and determine; a)V.R b)The effort if the incline is 72% efficient c)The work done against friction in raising the load through the height of 4m 14. The wheel and Axle It consists of a large wheel of radius R attached to an axle of radius r A car steering wheel, screw driver and some water taps are example of wheel and axle. The effort is applied on the wheel while the load is attached on the axle. 15. R-radius of the wheel, r-radius of axle Wheel Load r R Axle Effort V .R= Effort distance load distance V .R= Circumferenceof thewheel Circumferenceof axle V .R= 2( pie)R 2( pie)r V .R= R(radiusof wheel) r (radiusof axle) 16. Quiz A wheel and axle is used to raise a load of 28kg by a force of 40N applied to the rim of the wheel. If the radius of the wheel is 0.7m while that of axle is 5cm, calculate: (a)M.A (b)V.R (c)Efficiency 17. The screw R pitch Pitchisthedistancebetweentwosuccessivethreads V .R= Circumferenceof screwhead pitch V . R= 2( pie)R pitch 18. Quiz A car whose weight is 16000N is lifted with a jack-screw of 11mm pitch. If the handle is 0.28m from the screw and the force applied by the jack is 110N, find: (a)V.R (b)M.A (c)E 19. Gears Is a wheel that can rotate about its centre Driver-the effort wheel (where the effort is applied Driven wheel-is the load wheel 24 12 Effort Load V .R= no of teethof drivenwheel no of teethof driving wheel V .R= revolutionsmadeby driverwheel revolutionsmadeby drivenwheel 20. Quiz A driving gear wheel having 25 teeth engages with a second wheel with 100 teeth. If the gear system is 85% efficient, find: (a)V.R (b)M.A 21. Pulley belts Has both industrial domestic uses e.g. in posho mills, sewing machines, and motor engines Driving pulley Effort Load belt Driven pulley R r V .R= radiusof driven pulley radiusof driving pulley V . R= r R 22. Pulleys Is a wheel with a groove to accommodate a string. Three common pulley systems include: (a)Single fixed (b)Single movable (c)Block and tackle -In determining V.R of pulleys, count the # of-In determining V.R of pulleys, count the # of ropes supporting the loadropes supporting the load oror the # of upwardthe # of upward arrows.arrows. 23. Single fixed Pulley is fixed Effort and load moves thro' the same distance hence; V.R = 1, Effort=Load Load Effort 24. Quiz Refer previous figure, a pulley used to raise a load of 50N What is the V.R of the system Determine the M.A 25. Single movable Pulley is movable V.R = 2 Load Effort 26. Block and tackle Has more than two pulleys V.R=4 27. Graph of M.A vs Load for pulleys 28. Graph of Efficiency vs Load for pulleys 29. Quiz 1 Determine the V.R of the following pulley systems 30. Quiz 2 A pulley system having a velocity ratio of 4 is used to raise a load of 80N through height of 0.6m at a constant speed using an effort of 20N in a time of 15seconds. (a)Draw the diagram to show the pulley system. (b)Calculate the M.A of the pulley system (c)Find the efficiency (d)Calculate the power developed by the effort. 31. Assignment A pump can raise 120kg of water to height of 10m every minute. (a)What is the power output of the pump (b)If the efficiency is 80%, what power must be supplied to the pump. Hint: Efficiency= power output powerinput 100 32. Hydraulic press x