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The diagram below clearly shows a state of
equilibrium. The cars on
either side of the seesaw are exactly the same in weight and height, in fact
they are the same model. As a result the seesaw stays level. The weight (the cars) is called the effort. |
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The cars are in a 'state of equilibrium' because the weight on either side is exactly the same |
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If an extra car is added to the right hand side (see diagram to right) then the seesaw will turn in a clockwise direction - called a clockwise moment.Alternatively, if more cars are added to the left hand side the seesaw will turn in an anticlockwise direction - called an anticlockwise moment.
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| A clockwise moment as an extra car is added to the right side | |
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If the seesaw is to be in equilibrium then the clockwise moments must be equal to the anticlockwise moments. |
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QUESTIONS |
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1. The diagram below shows a lever where an effort of 200 N balances a load of 600 N. The effort force is 6 metres from the fulcrum. The load force is two metres from the fulcrum. |
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Clockwise moment = 600 x 2 Nm Anti-clockwise moment = 200 x 6 Nm In a state of equilibrium, clockwise moments = anti-clockwise moments 600 X 2 Nm = 200 x 6 Nm 1200 = 1200
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2. In the diagram below a crow-bar is used to move a 400n load. What effort is required to move the load? |
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Clockwise moments = 400 N x 0.6 m Anticlockwise moments = effort x 1.5m In equilibrium; clockwise moments = anti-clockwise moments 400 x 0.6 = effort x 1.5 effort = 400 x 0.6 1.5 effort = 240 1.5 = 160 N
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