Per8_exercise

# Per8_exercise - Period 8 Exercises E.1 A machine that is so...

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Period 8 Exercises E.1 A machine that is so well built that friction and other energy losses may be ignored is used to perform a task. The amount of work required to perform the task is __________ the amount of work required without the machine. a) less than b) more than c) the same as E.1 = c E.2 Susan raises an 800 lb upright piano 10 feet to the second floor of her house by using a frictionless pulley system. If she raises the piano by exerting a force of 50 lbs on the rope, what length of rope will she have to pull through the pulley? F in x D in = F out x D out = = in out out in F D F D E.2 = d 800 lbs x 10 ft = 160 ft 50 lbs 8-Ex 1&2

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E.3 What is the efficiency of a lever if 5 newtons of force are required to move the end of the lever arm 30 cm, which lifts a load of 10 newtons a distance of 5 cm? a) 3% b) 8% c) 33% d) 83% e) 300% Eff = Work out = F out D out = 10 N x 5 cm = 50 = 1 Work in F in D in 5 N x 30 cm 150 3 E.3 = c 8-Ex 3
E.4 In his job as a bricklayer, Ian must move a load of bricks to the top of a building. There are two winches Ian can choose to

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Per8_exercise - Period 8 Exercises E.1 A machine that is so...

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