Work, Power, & Simple Machines

An ax is an example of a(an)

• inclined plane

• wedge

• lever

• wheel and axle

A 120-m long ski lift carries skiers from a station at the foot of a slope to a second station 40 m above. What is the IMA of the lift?

• 0.3

• 3

• 40

• 160

A 750-W motor might also be rated as a

• 0.5-horsepower motor

• 1-horsepower motor

• 2-horsepower motor

• 10-horsepower motor

A mechanical device requires 420 J of work to do 230 J of work in lifting a crate. What is the efficiency of the device?

• 0.5%

• 55%

• 190%

• 183%

How can you make the work output of a machine greater than the work input?

• by decreasing friction

• by increasing the output distance

• by increasing the input force

• none of the above

The efficiency of a machine is always less than 100 percent because

• a machine cannot have an IMA greater than 1

• some work input is lost to friction

• the work input is too small

• the work output is too great

Tags

NGSS.MS-PS3-5

The power of a machine measures

• its rate of doing work

• the force it produces

• its strength

• the work it does

The actual mechanical advantage of a machine

• cannot be less than 1

• decreases as the input distance increases

• increases with greater friction

• is less than the ideal mechanical advantage of the machine

If you exert a force of 700 N to walk 6 m up a flight of stairs in 6 s, how much power do you use?

• 19 W

• 700 W

• 25,200 W

• 4200 W

Tags

NGSS.MS-PS3-4

NGSS.MS-PS3-5

A 750-W motor might also be rated as a:

• 0.5 horsepower motor

• 1 horsepower motor

• 2 horsepower motor

• 10 horsepower motor