# Introduction to Energy

ENERGY
An introduction
1 / 30
Slide 1: Tekstslide
G7 ScienceSecondary EducationAge 12

In deze les zitten 30 slides, met interactieve quizzen, tekstslides en 1 video.

## Onderdelen in deze les

ENERGY
An introduction

#### Slide 1 -Tekstslide

What is energy?
• Energy is the ability to do work or cause change in matter.
• In other words:
• Work is the transfer of energy to an object by a force that causes the object to move in the direction of the force.
• Energy is a property of all matter and all matter has energy.

#### Slide 2 -Tekstslide

For example
The boy is pushing the box.
The push is a force to make the box move.
The boy is using energy from his body to do this.
Energy is transferred to the box and it moves along the floor.

#### Slide 3 -Tekstslide

We can measure energy in terms of work done.
Work (j) = Force (N) x distance (m)
j = joules N = Newtons m = meters

#### Slide 4 -Tekstslide

How much work is done when you lift an apple (which weighs 2N) 3 meters off the ground?

#### Slide 5 -Open vraag

What is the relationship between work and distance?
As the distance an object moves increases ...
... the work needed to move the object increases.

Work is directly proportional to the distance moved.

#### Slide 6 -Tekstslide

SUMMARY
• Energy is the ability to do work and work requires a transfer of energy.
• Energy is transferred every time work is done.
• Energy and work are both measured in joules (J).
• If an object does not move (d = 0m) then no work is done.

#### Slide 7 -Tekstslide

What is energy?
A
Energy is a push.
B
Energy is the ability to do work.
C
Energy is the ability to attract objects.
D
Energy is a pull.

#### Slide 8 -Quizvraag

What is the equation to calculate work?
A
W = d/F
B
W = Pt
C
W = Fd
D
W = F/d

#### Slide 9 -Quizvraag

What is the unit of work and energy?
A
Watt
B
meter
C
Newton
D
joule

#### Slide 10 -Quizvraag

A force of 25N is used to push a box along the floor a distance of 5 meters. How much work was done?
A
125J
B
135J
C
145J
D
155J

#### Slide 11 -Quizvraag

It took 100J to push a chair 4 meters across the floor. What was the force used to push the chair?
A
15N
B
25N
C
15J
D
25J

#### Slide 12 -Quizvraag

A force of 50N was used to lift a rock. A total of 160J of work was done. How far was the rock lifted?
A
1.8m
B
2.3m
C
3.2m
D
4.1m

#### Slide 13 -Quizvraag

Mr. Nicholson pushed on a box with a force of 10,000N, but he was unable to move it. How much work was done?
A
0J
B
5,000J
C
10,000J
D
20,000J

#### Slide 14 -Quizvraag

What is a force?
• You will sometimes need to calculate the force before you can calculate work (W = Fd).
• A force is a push or a pull on an object.

#### Slide 15 -Tekstslide

What is weight?
• Weight is a force that depends on the acceleration due to gravity on an object and the object's mass. The object is pulled towards the center of Earth
• It is easy to confuse weight and mass.
• Mass (kg) is the amount of matter (atoms) an object contains.
• Weight (N) is the pull of gravity on an object.

#### Slide 16 -Tekstslide

How do we calculate force?
Force (N) = mass (kg) x acceleration (m/s/s)

*acceleration on Earth is 9.8 m/s/s

#### Slide 17 -Tekstslide

Calculate the weight of a box that is 55 kilograms.
A
240N
B
385N
C
420N
D
539M

#### Slide 18 -Quizvraag

An object accelerates at 5.0 m/s/s and it has a mass of 4.0 kilograms when an unknown force is applied to it.
What is the amount of the force?
A
5N
B
15N
C
20N
D
25N

#### Slide 19 -Quizvraag

An object accelerates at 10 m/s/s when a force of 20N is applied to it.
What is the mass of the object?
A
1kg
B
2kg
C
3kg
D
4kg

#### Slide 20 -Quizvraag

An object with a mass of 10kg has a force of 2N applied to it.
What is the acceleration of the object?
A
0.1 m/s/s
B
0.2 m/s/s
C
0.3 m/s/s
D
0.4 m/s/s

#### Slide 21 -Quizvraag

What is power?
Power is the distribution of energy over a period of time.
In other words ...
... it is the rate of doing work or
... how much work is done over a period of time

#### Slide 22 -Tekstslide

How is power calculated?
Power (W) = Work (J)/time (s)
W = Watt  J = joule  s = second

#### Slide 23 -Tekstslide

What is the power of a microwave oven if it can perform 4,000J of work in 10 seconds?
A
400W
B
500W
C
600W
D
700W

#### Slide 24 -Quizvraag

A box weighs 100N. It is lifted 4 meters in 20 seconds.
How much power is used?
A
10W
B
15W
C
20W
D
25W

#### Slide 25 -Quizvraag

What is the power output of a person that pushes a box 7 meters in 5 seconds with a force of 10N?
A
8W
B
10W
C
12W
D
14W

#### Slide 26 -Quizvraag

How much work is done using a 250W blender for 2 minutes?
A
15,000J
B
25,000J
C
30,000J
D
35,000J

#### Slide 27 -Quizvraag

Key Equations
1. Work (J) = Force (N) x distance (m)
2. Force (N) = mass (kg) x acceleration (m/s/s)
3. Power (W) = Work (J)/time (s)

#### Slide 28 -Tekstslide

A machine uses 150W of power to move a box 20m in 20s. Find the force needed and the work done by the machine and the mass of the box.

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