Work and Machines

Assume you push a 50-Newton box over a distance of 2 meters. How much work have you done?

• 100 J

• 50 J

• 25 J

• 2 J

An example of a machine that changes the direction of the applied force is a

• flagpole pulley

• doorknob

• nutcracker

• hammer

What is the ideal mechanical advantage of a machine that has an input distance of 5 meters and an output distance of 10 meters?

• 1/2

• 1

• 2

• 5

What is the actual mechanical advantage of a machine that has an input distance of 5 meters and an output distance of 10 meters?

• less than 1/2

• greater than 1/2

• greater than 1

• greater than 2

Simple machines that have an ideal mechanical advantage greater than 1 include

• screws

• inclined planes

• wedges

• all of these

Which statement about compound machines is false?

• They have a greater mechanical advantage than simple machines

• They may consist of hundreds of simple machines

• They are more efficient than simple machines

• They include scissors and bicycles

How much work is done by a 1000-watt hairdryer in 40 seconds?

• 0.4 J

• 25 J

• 960 J

• 40,000 J

One horsepower is about equal to

• 1 watt

• 75 watts

• 745 watts

• 1 kilowatt

Machines that increase the distance over which force is applied include

• hammers

• doorknobs

• nutcrackers

• pry bars

Ways that machines make work easier include

• increasing force

• increasing work

• increasing efficiency

• all of the above