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1. Can you write the title of the new unit

Energy, work and power and date

2 . stick in the revision topic list.

3. How many types

(forms) of energy can you remember?

**Do now!**

James Prescott Joule

1818 - 1889

4 Books in at end of class

• Work done

• W.D =

Forces x distance in the direction of the force

.

• The

Joule J the unit for both energy and work done

• What is energy

• Types of energy

When any object is moved around work will need to be done on it to get it to move (obviously).

We can work out the amount of work done in moving an object using the formula:

Work done = Force x distance moved in direction of the force

W

*in J in N in m joules newtons meters*

F d

*Calculate the work done when a force of *

*5 newtons moves through a distance of *

*3 metres.*

**work = force x distance**

= 5N x 3m

**work = 15 joules**

*Calculate the work done when a force of *

*6 newtons moves through a distance of *

*40 centimetres.*

**work = force x distance**

= 6 N x 40 cm

= 6 N x 0.40 m

**work = 2.4 joules**

• Make Force the subject of the equation

F

W d

• Make distance the subject of the equation

*Calculate the value of the force required to do 600 joules of work over a distance of 50 metres.*

**work = force x distance**

*becomes:*

**force = work done **

**÷ distance **

= 600 J

÷

50 m

**force = 12 newtons**

*Calculate the distance moved by a force of *

*8 newtons when it does 72 joules of work.*

**work = force x distance**

*becomes:*

**distance = work done **

**÷ force**

= 72 J

÷

8 N

**distance moved = 9 metres**

1. Bori pushes a book 5m along the table with a force of 5N.

He gets tired and decides to call it a day. How much work did he do?

2. Alicia lifts a laptop 2m into the air with a force of 10N.

How much work does she do?

3. Martin does 200J of work by pushing a wheelbarrow with a force of 50N. How far did he push it?

4. Chris cuddles his cat and lifts it 1.5m in the air. If he did

75J of work how much force did he use?

5. Carl drives his car 1000m. If the engine was producing a driving force of 2000N how much work did the car do?

Question 5

*Calculate the work done by a child of weight 300N who climbs up a set of stairs consisting of 12 steps each of height 20cm.*

**work = force x distance**

The child must exert an upward force equal to its own weight.

*Therefore:*

**force**

= 300N

This force is exerted upwards and so the distance must also be measured upwards.

= (12 x 20cm)

= 2.4m

*therefore:*

**work**

= 300 N x 2.4 m

**work = 720 J**

“The capacity to do work”

Not a very good definition!

Energy measurement

– Copy please

Energy is measured in

**joules (J)**

To lift an apple 0.1 kg upwards by one metre requires about one joule of energy.

1 kilojoule (kJ) = 1 000 J

10

3

J

1 megajoule (MJ) = 1 000 000 J

10

6

J

Energy can take many forms;

Now list the different types of energies in the following two groups

**Kinetic Energy **

**– movement energy **

**Potential Energy **

**– energy due to position or shape or stored energy **

Forms of energy

Energy can exist in many forms.

**1. THERMAL or HEAT ENERGY**

This is the energy of an object due to its temperature.

**2. LIGHT ENERGY**

This is energy in the form of visible electromagnetic radiation.

**5. KINETIC ENERGY**

This is the energy possessed by a moving object.

Kinetic energy increases is the object’s speed is increased.

Also often called ‘Movement energy’

A kicked football has 50J of energy

**3. ELECTRICAL ENERGY**

This is the energy transferred by an electric current.

**4. SOUND ENERGY**

This is energy in the form of a sound wave.

**6. CHEMICAL ENERGY**

This is energy that is released when chemical reactions take place.

Sources of chemical energy include: fuel, food and batteries.

Energy in one chocolate biscuit 300 000 J

Energy in the food you in one day 11 000 000 J

**7. NUCLEAR ENERGY**

This is energy that is released when nuclear reactions take place.

*This is the source of the *

*Sun’s energy.*

**8. POTENTIAL ENERGY**

This is the energy possessed an object due to its position.

**Gravitational Potential Energy**

The gravitational potential energy of an object increases if it is raised upwards.

**Elastic Potential Energy**

This is the energy stored in a stretched or squashed object

*- also known as strain energy*

Gravitational potential energy being converted into kinetic energy.

• A fully flexed bow stores around 300J of energy

Now list the different types of energies in the following two groups

**Kinetic Energy **

**– movement energy **

**Potential Energy **

**– energy due to position or shape or stored energy **

• Thermal

• Light

• Sound

• Electric

• Kinetic

• Chemical

• Gravitational

• Strain

• Nuclear

This means that the total amount of energy in the

Universe stays the same!

We can write energy flow diagrams to show the energy changes that occur in a given situation.

For example, when a car brakes, its kinetic energy is transformed into heat energy I the brakes.

Kinetic heat

When a rocket launches.

When a rocket launches.

Chemical kinetic + sound + heat gravitational

Around the room are a few examples of energy changes (some simple, some a little more complicated!)

For each example I want you to write the name of the experiment and then the energy flow diagram for that experiment

You will have 2 minutes on each example.

?