Work and Power

Power

Power is the rate at which something does work over a period of time

Multiple Choice

Work divided by time equals...

• energy
• power

Multiple Choice

The unit used to measure power is the 

• Watt
• Newton
• Joule
• Newton*meter

Multiple Choice

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

• 0.125 s
• 8 s
• 64800 s
• 80 s

Multiple Choice

Person A and Person B are both using the same amount of work to lift something. Person A takes half as much time to do it. Who has greater power.

• Person A

• Person B

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

The equations for work and power can be combined to simplify problem solving.

​Since W = Fd and P = W/t,

We can say that P = Fd/t

Work and Power

Multiple Choice

Which of the following would produce the most power?

• A mass of 10 kilograms lifted 10 meters in 10 seconds 
• A mass of 10 kilograms lifted 10 meters in 5 seconds
• A mass of 5 kilograms lifted 10 meters in 5 seconds
• A mass of 5 kilograms lifted 5 meters in 10 seconds

Multiple Choice

You move an 8-newton weight five meters in 4 seconds. How much power have you generated?

• 160 watts
• 10 watts
• 6.4 watts
• 17 watts

Remember! The faster the work is done, the more power. Energy is transferred faster too!

Match

Match the SI Unit to the measurement

• newton (N)

• joule (J)

• watts (W)

Force

Work

Power

• Force

• Work

• Power

An engine reaches its top speed in 7.5 s.
It performs 250,000 J of work in that time.
What is the engine’s power?

Given

(w/ Units):

Formula:

Substitution
(w/ Units):

Answer

(w/ Units):

An engine reaches its top speed in 7.5 s.
It performs 250,000 J of work in that time.
What is the engine’s power?

Given

(w/ Units):

Formula:

Substitution
(w/ Units):

Answer

(w/ Units):

work = 250,000 J

time = 7.5 s

P = w ÷ t

P = 250,000 J ÷ 7.5 s

33,333 W

More about POWER!

Can you change how much power you exert?

Yes! If you do work faster, then you will exert more power.

Practice is POWERful!

Open up those workbooks!

Complete section 6.1 review on pages 64-65.