5.2.1 Work Done

Work done

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Formula

\text{Work Done} = \text{Force} \times \text{Distance}

W = F \times s

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Key Points

Where Work Done, $W$ , is in joules $J$ , the force, $F$ , is in newtons (N), and the distance, $s$ , is in meters $m$ .
Where distance is the distance moved along the line of action of the force.

Definition

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Work done is when energy is transferred from the object doing the work to another form.

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Examples:

If a book is lifted 1m in the air and 2m to the right.
Work is done (against gravity) when moving 1m vertically, as that is in the direction of the force (gravity).
Energy is transferred from your muscles to the book, increasing its gravitational potential.

Joules

One joule of work is done when a force of one newton causes a displacement of one meter.
- $1 \text\ {joule} = 1 \text\ {newton-meter}$

Friction

Work done against frictional forces causes a rise in temperature of the object.

Work Done in a Spring

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Formula

\text{Work Done} = \frac{1}{2} k x^2

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Key Points

When a force stretches or compresses a spring, the spring does work.
Elastic potential energy is stored in the spring.
Provided it does not inelastically deform:
The work done on the spring equals the elastic potential energy stored.

Calculating Work Done

The amount of work done on an object due to a force can be calculated using the following equation:

W=Fs

$W$ is work done in Joules (J)
$F$ is force in Newtons, (N)
$s$ is the distance in metres (m).

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1J of work is done when a force of 1N moves an object through a distance of 1m. Therefore 1 Joule = 1 Newton-meter.

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Example: Calculating Work Done A man pushes a box through a distance of 12m, and he exerts 14N of force on the box. Calculate the work done by the man. Ignore the frictional force.

[2 marks]

Using the work done equation:

$W=Fs$

Substitute in the values:

$W$ =14×12

Calculate the answer:

$W$ =168J or Nm

Work Done Simplified Revision Notes for GCSE AQA Physics Combined Science

5.2.1 Work Done

Work done

Definition

Joules

Friction

Work Done in a Spring

Calculating Work Done

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