WORK DONE

• Science
• Lower Secondary (Key Stage 3)

Which of the following does not show work being done?

1. 
2. 
3. 
4. 

TOPIC: WORK, ENERGY AND MACHINES

In today's lesson you will learn to:

1. Describe what work is
2. Describe what simple machines are

WHAT IS WORK?

The energy transferred in order to move an object.

 Work is not a form of energy - it is one of the ways in which energy can be transferred.

unit for work

unit for force

unit for distance

Work done (joule, J) = force (newton, N) × distance moved (metre, m)

 W= F x d

We can rearrange the formula for work so we can calculate distance and force

Force = work done / distance

Distance = work done/ force

WORKED EXAMPLE 1

A boy throws a ball with a force of 70N over to his friend who is 3m away. Calculate the work done.

WORKED EXAMPLE 2

A girl does 500 J of work climbing a flight of stairs at a distance of 70m. Calculate her force.

1. 10 W
2. 10J
3. 10 m
4. 10N

1. 20J
2. 20m
3. 20 N
4. 20 W

Emily does work of 6 J, and pushes with
a force of 3 N, what distance does she
travel?

1. 3N
2. 3m
3. 18 m
4. 9J

WORK OUT THESE OUT IN YOUR BOOK. SHOW YOUR BOOK TO YOUR TEACHER FOR MARKING.

A. An office worker has a weight of 750N. He climbs the stairs 20m to his desk. Calculate the work done

B. A mechanic applies a force of 120N to lever to lift a car, moving the lever through a distance of 0.4 m. Calculate the work done

What is a simple machine?

A simple machine reduces the force needed to do a job or increases the distance that something moves when a force is applied.

LEVERS

PULLEYS

GEARS

Examples of simple machines:

LEVERS

A simple machine consisting of a beam or rigid rod pivoted at a fixed hinge.

LEVERS

Levers are force multipliers – this means it allows us to apply forces more conveniently, or to increase the effort of a force.

The PIVOT – where the lever turns

The EFFORT – the force being applied to lever

The LOAD – the force which is being moved

Shen kicks a ball with a force of 90N to a distance of 4m across the MUGA. Calculate the amount of work Shen did.

1. 360J
2. 22.5J
3. 94J

Which of the following is NOT an example of a lever?

1. 
2. 
3. 
4. 

What distance is moved if we have a 8N force and the work done is 90 J?

1. 720J
2. 11.25m
3. 0.08m

LEVERS

Levers are force multipliers – this means it allows us to apply forces more conveniently, or to increase the effort of a force.

The PIVOT – where the lever turns

The EFFORT – the force being applied to lever

The LOAD – the force which is being moved

LEVERS

A wheel barrow is an example of a lever

EFFORT

LOAD

PIVOT

Which answer describes the effort, load and pivot?

1. A- effort; B - pivot; c - load
2. A - load; B - effort; C - pivot
3. A - effort; B - load; C - pivot

Which answer describes the effort, load and pivot?

1. A- effort; B - pivot; c - load
2. A - load; B - effort; C - pivot
3. A - pivot; B - load; C -effort

Which answer describes the effort, load and pivot?

1. A- effort; B - pivot; c - load
2. A - load; B - effort; C - pivot
3. A - pivot; B - load; C -effort

Which answer describes the effort, load and pivot?

1. A- effort; B - pivot; c - load
2. A - load; B - effort; C - pivot
3. A - pivot; B - load; C -effort

Which answer describes the effort, load and pivot?

1. A- effort; B - load; c - pivot
2. A - load; B - effort; C - pivot
3. A - pivot; B - load; C -effort

HOW WAS THIS LESSON?

😒🙁😐🙂😃