3.2 Machines & Work

Multiple Choice

A ___________ is a device that changes the force or increases the motion from work.

• Work

• Job

• Machine

• Calculator

Multiple Choice

The purpose of machines is to _______________.

• Make us look cool

• Make work easier

• Change the way work is done

Multiple Choice

_____________ is a measure of how much of the work is changed into useful work

• Efficiency

• Energy

• Joule

• Newton

Multiple Choice

What is the equation for efficiency (%)

• output work divided by input work x 100

• input work divided by output work x 100

• output work divided by net force x 100

• Input work divided by net force x 100

Multiple Choice

Machines can be made more efficient by ____________.

• Increasing input

• Decreasing energy

• Increasing friction

• Reducing friction

Multiple Choice

Machines change the way work is done in what way?

• change the direction of a force

• Increase force

• All of the above

Multiple Choice

What is the SI unit for work?

• Newtons

• Joules

• Grams

Fill in the Blank

_______ = output force / input force

Multiple Choice

What is the mechanical advantage for a crate that weighs 950 N and is lifted with a pulley force of 250 N.

• 1.5

• 2.0

• 3.8

• 4.0

Multiple Choice

You do 20 J of work in pushing a crate up a ramp. If the output work from the inclined plane is 11 J, then what is the efficiency of the inclined plane?

• 55%

• 45%

• 55J

• 55N