Simple Machines, Mechanical Advantage & efficiency

The amount by which a machine multiplies input force is known as the 

• work.
• power.
• output force.
• mechanical advantage.

A screwdriver is an example of a wheel and axle, which is a type of simple machine. The mechanical advantage of a wheel and axle is the ratio of the radius of the wheel to the radius of the axle. The force required to turn a screw can be reduced by

• reducing the length of the axle.
• increasing the radius of the axle.
• reducing the length of the handle.
• increasing the radius of the handle.

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NGSS.MS-PS2-1

Elevators lift loads by employing a motor and a complex system of pulleys. If the elevator converts all the energy used to work (no heat or friction is generated), how many Joules would be required to lift a 2,500 N load 15 m? This is about five floors in a typical building.

• 1637 J
• 3827 J
• 37500 J
• 167 J

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A lever and fulcrum are used to lift a fallen tree, which has a weight of 480 N. If the lever has a mechanical advantage of 5.5, what is the input force that will begin lifting the tree off the ground?

• 5.5 N
• 40.7 N
• 87.3 N
• 2640 N

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NGSS.MS-PS2-1

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What is the primary mechanical advantage of using the simple machine seen in the image?

• You can apply a small input force and have it multiplied into a large output force.
• You can apply a large input force and have it multiplied into a small output force.
• You can apply a small input distance and have it multiplied into a large output distance.
• You can apply a large input distance and have it multiplied into a small output distance.

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NGSS.MS-PS2-1

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What is the ideal mechanical advantage of an inclined plane which has 4 cm height and 16 cm slope?

• 1/4
• 1
• 16
• 4

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What is the efficiency of a machine if 55.3 J of work are done on the machine, but only 14.3 J is produced by the 1machine?

• 0.25 J
• 26%
• 386%
• 3.86 J

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NGSS.MS-PS3-5

What is the efficiency of the machine if the input is 263 J and the output is 142 J? 

• 6.26%
• 54%
• 100%
• 260%

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A machine has a work output of 8 joules and requires 10 joules of work input to operate. What is the machine's efficiency?

• 8 J
• 10 J
• 80%
• 800%

What is the mechanical efficiency of a machine whose work input is 250 J and work output is 30 Joules??

• 12 % ME
• 83 % ME 
• .12 % ME 
• .83% ME