2.7 Energy & Power

Open Ended

Proverbs and Folklore are useful ways of teaching, and passing down stories and traditions in many cultures.

COMPLETE THIS MADE UP PROVERB WITH A FUNNY ANSWER..

"One who forgets what he learned ............................."

Did you forget what you learned?

Lets find out!

So far in this unit, We've talked about;

• Energy resources (renewables & non renewables)

• Radiation (Heat transfer in a vacuum)

• Conduction & convection (Heat transfer through particles)

• Temperature

• Conservation of energy (Energy stores & transfer)

• Forms of energy (definitions & motion caused by each)

Poll

How many of the lessons on the previous page do you remember?

• Energy resources (renewables & non renewables)

• Radiation (Heat transfer in a vacuum)

• Conduction & convection (Heat transfer through particles)

• Temperature

• Conservation of energy (Energy stores & transfer)

  +

  Forms of energy (definitions)

Review questions!

Complete these recap questions to check what you already remember.

Multiple Choice

__________ is the transfer of energy through a medium such as liquid or a gas.

• Convection

• Conduction

• Radiation

Multiple Choice

___________ is the transfer of energy through a wave.

• Convection

• Conduction

• Radiation

Multiple Choice

_________ is the transfer of energy through direct contact.

• Convection

• Conduction

• Radiation

Multiple Choice

Particles are spaced the farthest apart in _______ and the closest together in _______ .

• solids;gases

• solids;liquids

• gases;liquids

• gases;solids

Multiple Choice

What is an example of kinetic energy?

• A bird sitting in a tree

• A bouncy ball on the table

• A car driving on the highway

• A book on shelf

Multiple Choice

What is an example of potential energy?

• A bowling ball rolling down a lane

• A car parked in a lot

• An apple falling from a tree

• Sunlight heating up the atmosphere

Multiple Choice

Total energy will always change in a system of objects.

• True; energy is destroyed due to friction

• False; energy cannot be destroyed, only transferred.

Multiple Select

Which of the following describes an energy transformation?

• When energy is lost due to friction

• An electric motor moving a car

• A solar panel powering a home

• A television projecting a show

Multiple Choice

What is energy? What are its units?

• The strength of a person, Joules

• The motion of a particle, Kilograms

• The amount of force, Newtons

• The ability to do work, Joules

Multiple Choice

Which type of energy involves moving molecules?

• Atomic

• Nuclear

• Electric

• Thermal

Multiple Choice

The average kinetic energy of the molecules of a substance is known as __________?

• Speed

• Temperature

• Mass

• Volume

2.7 Energy and Power

Use pages 152-153 to complete this lesson;

Lesson objectives;

1. Explain the difference between energy and power

2. Describe the link between power, fuel use, and the cost of using domestic appliances

Multiple Choice

Consider this scenario. Lets assume there are no distractions at all.

Taji takes 3 minutes to return 10 laptops from class to the IT lab.

Thirza takes 2.5 minutes to do the same task.

Who does more work?

• Taji, he takes more time

• Thirza, she takes less time

• They do the same amount of work because they are doing the same task

• They both don't do any work

Multiple Choice

Consider this scenario. Lets assume there are no distractions at all.

Taji takes 3 minutes to return 10 laptops from class to the IT lab.

Thirza takes 2.5 minutes to do the same task.

Who exerts more power?

• Taji, he takes more time

• Thirza, she takes less time

• They exert the same Power because they are doing the same task

Multiple Choice

Kyle's horse plough a field in two days.

Elisha's horse takes just 1 day to plough the same field.

Which horse does more work?

• Kyle's, because it takes more time

• Elisha's, because it takes less time

• They do the same amount of work because its the same task

• They both do 0 work

Multiple Choice

Kyle's horse plough a field in two days.

Elisha's horse takes just 1 day to plough the same field.

Which horse has more power?

• Kyle's because it takes more time

• Elisha's, because it takes less time

• Same power because its the same task

• We can't measure their power.

POWER

Power is how fast work is done.

OR

How fast energy is transferred.

In science terms;

Power is the rate of energy transfer.

Multiple Select

Define power. (Select all correct answers)

• The rate of doing work

• How fast work is done

• The rate of energy transfer

• How fast energy is transferred

Multiple Choice

It is the rate of doing work

• Energy

• Power

• Force

• Acceleration

Multiple Select

How do you calculate power? (Select two answers)

• P = Work/t

• P = Energy/t

• P = work * t

• P = Time/Energy

Multiple Select

What does the word "rate" mean in science? (Select all that apply)

• How fast something happens

• How quickly something happens

• Speed of something

• The weight of something

Multiple Choice

Page 152; Why do some microwaves cook popcorn faster that others?

• Because they are bigger

• Different brands

• Depends on how old they are

• Different power rating

Multiple Select

Page 152; Complete the sentence; (select two answers)

The power rating of an appliance tells you;

• ...the power of a microwave

• ....how much energy is transferred per second

• ...... the rate of energy transfer

• ...how to calculate the power

Multiple Choice

The unit of Power is;

• Joules

• Newtons

• Kilograms

• Watts

Multiple Choice

Power is the rate of energy transfer.

You can calculate power using the equation;

• Power = Energy x Time

• Power = Work x Time

• Power = Energy ÷ Time

• Power = Time ÷ Energy

Multiple Choice

Taji takes 3 minutes to do 600J of work t return laptops to the IT lab. How much power does Taji have? (Time must be converted to seconds)

• 3.3 Watts

• 200 Watts

• 0.2 Watts

• 600 Watts

Multiple Choice

Thirza takes 2.5 minutes to do the same task of work to return laptops to the IT lab. How much power does Thirza have? (Time must be converted to seconds)

• 4 Watts

• 3.3 Watts

• 0.2 Watts

• 5 Watts

Multiple Select

What is the difference between power and energy

• Energy is the ability to do work, Power is the rate at which that work is done

• Energy is the rate of doing work, Power is the capacity at which work is done

• Energy is measured in Joules, Power is measured in Watts

• Energy is not conserved but power is conserved

Multiple Choice

Two workers use 100 N of force to move a sofa 2 meters in 2 seconds. How much power is required?

• 100 watts

• 400 watts

• 104 watts

• 50 watts

Multiple Choice

How do we calculate work?

• W = Force * distance

• watts = force * Distance

• W = Force * Density

• watts = force * density

Multiple Choice

You do 40 Joules of work in 8 seconds. How much power did you exert?

• 0.2 watts

• 320 watts

• 5 watts

Multiple Select

What is needed calculate power?

• work

• time

• mass

• distance

Multiple Choice

The more POWER you use to move an object, the more work you do. 

• True

• False

Multiple Choice

Two workers use 200 J of work (energy) in 2 seconds. How much power is required?

• 100 watts

• 400 watts

• 104 watts

• 50 watts

Multiple Choice

How much power is used if 350 Joules of work is used to push a box a distance for 5 seconds?

• 70 watts

• 1750 watts

Multiple Choice

How much power is used if a force of 35 Newtons is used to push a box a distance of 10 meters in 5 seconds? (Hint: Solve for work first. This is a 2-step problem.)

• 70 W

• 3.5 W

• 7 W

• 350 J

Multiple Choice

A set of pulleys is used to lift a piano weighing 1,000 newtons.  The piano is lifted 3 meters in 60 seconds  How much power is used? (Hint: This is a two step problem.)

• 16.67 watts

• 50 watts

Multiple Choice

What is the difference between calculating power and work?

• Power takes into account the time it takes to complete a task

• Work takes into account the time it takes to complete a task

• Power is force/area

• Work is force/area

Open Ended

Page 152; Fill in the blanks

All hot objects cool down. To keep a house at the ___ temperature, you need to transfer ___ to it at the ___ ___ as energy is being transferred from it.

Multiple Choice

TRUE / FALSE; Page 152

When you pay an electricity bill, you are paying for fuel such as coal to be burnt at a power station.

• TRUE

• FALSE

Multiple Choice

Fill in the blanks; Page 152

You are charged for the number of ___ that you use for each appliance, and for the ___ of each appliance

• days, power

• hours, power

• hours, energy

• days, energy

Multiple Choice

TRUE / FALSE; Page 152

You calculate energy use in Kilowatt hours

• TRUE

• FALSE

Multiple Choice

State the unit of energy that electricity companies use

• Watts

• Hours

• Joules

• Kilowatt Hours

Multiple Choice

Page 153; Calculate the amount of energy used by 10 Kilowatt hours

• 43,200,000 Joules

• 1000 Joules

• 3600 Joules

• 36,000,000 Joules

Multiple Select

Page 153; To reduce your energy bills; (Select all correct answers)

• Use fewer appliances

• Use appliances that require less power

• Use appliances for fewer hours

• Buy cheaper gadgets