# Investigating Hooke’s Law

This is an example of a common experiment used to investigate Hooke’s Law. It should help you understand how to work scientifically.

## Aim of the experiment

To investigate how adding mass to a spring affects its extension.

## Method

1. Set up the apparatus as in the diagram
2. Add a 10 g mass to the holder and record the spring length.
3. Add another 10 g mass and record the new spring length.
4. Take away the previous spring length from the new length to calculate the extension (the difference).
5. Repeat by adding 10 g masses until 100 g is reached.
An experiment to investigate Hooke’s Law

## Variables

• The independent variable is the mass.
• The dependent variable is the extension.
• Controlled variables include using the spring and masses used.

## Risks

Care must be taken with masses.

## Expected results

Mass usedForceSpring lengthExtension
0 g0 N20 mm20 mm
10 g0.1 N25 mm5 mm (25 - 20 = 5)
20 g0.2 N30 mm5 mm
30 g0.3 N35 mm5 mm
40 g0.4 N40 mm5 mm
50 g0.5 N46 mm5 mm

## What the results mean

The spring extended 5 mm each time a 10 g mass is added (which increased the force due to gravity by 0.1 N). This follows Hooke’s Law which states that the extension of an elastic object (like a spring) is directly proportional to the force added.

## Evaluation

• Your measurements are accurate if they are close to their true value.
• Your measurements are precise if they are similar when completed again.
• Your experiment is repeatable if you get precise measurements when it is repeated.
• Your experiment is reproducible if others get precise measurements when they repeat it.
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