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WORK AND MACHINES 8 TH GRADE SCIENCE

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100 200 400 300 400 Choice1Choice 2Choice 3Choice 4 300 200 400 200 100 500 100

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Row 1, Col 1 A runner exerts 200N of force over 3 meters and generates 300 watts of power. How long did it take the runner to do this? Power = F x D / Time What is 2 seconds?

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1,2 Name an example of a wedge. What is ax, zipper, shovel?

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1,3 The force that is used over a distance to move an object is called__________. What is a work?

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1,4 A fixed point that a lever pivots around and where it is supported is called _______. What is a fulcrum?

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2,1 Name an example of a wheel and axle. What is a screwdriver, door knob, steering wheel?

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2,2 This is a device that allows you to do work easier. What is a machine?

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2,3 A newton-meter is also called________? What is Joule?

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2,4 Name 3 factors in which a machine makes work easier and give an example of each. What is change the amount of force you exert, change the distance over which you exert force, or change the direction in which you exert the force? Ramps helps you to exert a smaller force over a longer distance. A bike gear helps you exert a greater force over a shorter distance. A pulley lets you change the direction.

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3,1 This multiples effort force over a long distance________. What is a screw?

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3,2 If you do 2,000J of work and your simple machine does 500J, what is the efficiency of the simple machine? OW/IW x 100% What is 25%?

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3,3 On your leg, the fulcrum is at your_______? What is knee?

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3,4 This uses 2 or more machines. What is a compound machine?

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4,1 A relatively small unit of power is called ________. What is a watt?

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4,2 A force of 30 N moves an object a distance of 5 meters. How much work is done? Work=(force)(distance) 150J

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4,3 You use 5 N to move a 10 N object using a pulley. What Is the AMA? AMA=Output force/input force 2

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4,4 For work to be done, the direction of the applied force must be in the same or different direction of the motion? What is the same?

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5,1 Does friction make a simple machine more or less efficient? less

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5,2 If a 200 N person goes 5 m in 2 seconds. What is their power? P= F X D/T 500 W

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5,3 Comparing output work to input work as a percent will give you the ______________ of a machine? What is efficiency?

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5,4 The ideal machine has the efficiency of what %? What is 100%.

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