Work, Power and Mechanical Advantage

Work, Power and Mechanical Advantage

Multiple Choice

A crocodiles teeth would be most similar to what type of simple machine?

• lever

• wheel and axil

• wedge

• inclined plane

Multiple Choice

Which of the following does a screw do?

• lifts things

• separates things

• holds things together

• none of the above

Multiple Choice

what splits things apart?

• lever

• wedge

• wheel and axle

• screw

Multiple Choice

What is the equation for force?

• F= mass × acceleration

• F = mass × distance

• F= distance/time

• F = mass/time 

Multiple Choice

What is the unit of measurement for force?

• Joule

• meters

• time

• Newton

Write this part down on page 116

Work - Using a force to move an object some distance.

Work = Force x Distance W=FD

Work is measured in Joules (J)

Multiple Choice

Which of the following is an example of work being done?

• Teacher sitting in a chair

• Book resting on desk

• Keys hanging from a key chain

• A ball being rolled on the floor

Fill in the Blanks

If a student uses 20 Newtons of Force to push a chair 5 meters, how much is work is being done?

_ Joules

Multiple Choice

What is the unit of measurement for work?

• Newtons

• Joules 

• Watts

• Meters

Fill in the Blanks

If a lion drags his prey 10 meters to his den doing 500 joules of work, how much force did he use?

_ N

Multiple Choice

Which would be most effective to push a heavy box into a truck?

• super cow

• inclined plane

• wedge

• pulley

Multiple Choice

How is work defined?

• the amount of energy 

• the transfer of force over a distance

• rate of work in a given time

• the change in distance in a given time

Back to page 116!

Power - How much work is done over time.

Power = Work/Time P=W/t

Power is measured in Watts. 1W = 1J/s

Multiple Choice

Which variable DOES NOT determine the amount of work done on an object?

• joules

• force

• time

• distance

Multiple Choice

What units are used for power?

• joules

• seconds

• Newtons

• watts

• meters

Multiple Choice

Your car is stuck in the mud. You push with 500 N of force but it never moves. How much work did you do?

• 0 J

• 500 J

• 500 N

• 0 N

Multiple Choice

You do 90 joules of work in 30 seconds. How much power have you generated?

• 30 watts

• 3 watts

• 120 watts

• 270 watts

Fill in the Blanks

How much time is needed to produce 720 Joules of work if 90 watts of power is used? 

Seconds

Fill in the Blanks

A 70 watt light bulb runs for 15.0 seconds. How much energy does it use?

_ J

Fill in the Blanks

How much power does it take to lift 15.0 N 10.0 m high in 6.00 s?

_ W

Multiple Choice

No machine in existence has 100% efficiency due to ____________________.

• magic

• friction

• smoke

• input

Back to 116

Mechanical Advantage = the number of times a machine increases input force.

MA = output force/input force

Fill in the Blanks

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?

Multiple Choice

What is mechanical advantage?

• The advantage a machine has over a bicycle

• A measure of how much a simple machine reduces work

• A measure of when is the best time to use a simple machine

• the number of times a machine increases input force

Multiple Choice

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

• Yes

• No

Fill in the Blanks

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?

Multiple Choice

A machine's __________________ is the number of times the machine multiplies the input force.

• power

• force

• mechanical advantage

• efficiency

Multiple Choice

A machine's __________________ is the amount of work input that is turned into work output.

• power

• force

• mechanical advantage

• efficiency