Mechanical Advantage Review

How can machines help you do work?

• Change the amount of force you're using

• Change the amount of work you're doing

• Change the direction of your force

• Change the distance you move something

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In a real-world machine, what is true about work in compared to work out?

• Work In > Work Out

• Work In = Work Out

• Work In < Work Out

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You push down on a lever with a force of 100 N to lift a 500 N box.

What is the input force?

• 100 N

• 500 N

You push down on a lever with a force of 100 N to lift a 500 N box.

What is the mechanical advantage of the lever?

(a)  

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You have a lever with a mechanical advantage of 5.

What is most likely its ideal mechanical advantage?

• 6

• 5

• 4

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Is it possible to have a machine in the real world with 110% efficiency?

• Yes

• No

As a percent, what is the efficiency of a machine that puts out 90 J of work when you put in 100 J of work?

(a)  

Which of the following machines loses the most energy to heat?

• 50% efficient machine

• Output Work = 60 J

  Input Work = 100 J

A machine's efficiency can be improved by reducing friction.

What can you do to reduce friction in a machine?

What does friction produce that reduces efficiency?

• heat

• water

• energy

• work