AQA · GCSE · Combined Science · Higher

Spring extension from elastic energy

Q05.4 3 marks

The spring can store a maximum of 1800 J of elastic potential energy before it becomes inelastically deformed.

Calculate the maximum extension of the spring before the spring becomes inelastically deformed.

spring constant = 225 N/m

Use the Physics Equations Sheet.

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Marking points

1 Use the elastic potential energy equation and substitute $E_e=1800\ \text{J}$ and $k=225\ \text{N/m}$ .
2 Rearrange correctly for the extension, including the square root.
3 Give the maximum extension as $4\ \text{m}$ .

Full-mark answer

Using $E_e=\frac{1}{2}ke^2$ : $1800=\frac{1}{2}\times225\times e^2$ . Therefore $e=\sqrt{\frac{2\times1800}{225}}=4\ \text{m}$ .

Why this answer loses marks

$16\ \text{m}$

This is $e^2$ , not $e$ ; the square root has not been taken.