GCSE Questions - Hooke's Law

Q4. The diagram shows a child on a playground toy.

(a) The springs have been elastically deformed.

Explain what is meant by 'elastically deformed'.

Elastically deformed means that the speings will return to their original shape/length when the force (weight of the child) is removed.

[2 marks]

(b) Meghan investigated the relationship between the force applied to a spring and the extension of the spring. The graph below shows the results.

(a) Use the graph to determine the spring constant of the spring.

Spring constant = Force/extension

k = F/Δx

k = 4.0/0.10

Any correct pairs of readings from the graph were allowed

k = 40 N/m

[4 marks]

(b) Meghan concluded: ‘The extension of the spring is directly proportional to the force applied to the spring.’ Explain how the graph supports the her conclusion.

The line is straight and passes through the origin.

[2 marks]

(c) She repeated the investigation using a different spring - one with a spring constant of 13 N/m. Calculate the elastic potential energy of this spring when its extension was 20 cm.

Work done in stretching the spring = area under the force extension graph

Energy stored = ½FΔx

F = kΔx

Energy stored = ½k(Δx)²

Energy stored = ½ x 13 (0.20)²

Energy stored = 0.26 J

[3 marks]

(d) Describe a method Meghan could have used to obtain the results given in the graph above.

You should include a risk assessment for one hazard in the investigation.

Your answer may include a diagram.

This type of question is marked in two ways:

- the examiner looks for relevant instructions

- but also for the correct order - and any opposing instructions make you lose marks!

It is not just a 'tick fest' - but a marker does look to see how many relevant points you have made, then considers how you have strung them together to put your answer into a 'level'

 

Possible diagram

Indicative content they looked for:

set up a clamp stand with a clamp
hang the spring from the clamp
use a second clamp and boss to fix a (half) metre ruler alongside the spring
record the metre ruler reading that is level with the bottom of the spring
hang a 2 N weight from the bottom of the spring
record the new position of the bottom of the spring
calculate the extension of the spring
measure the extension of the spring
add further weights to the spring so the force increases 1 N at a time up to 5 N
for each new force record the position of the bottom of the spring and calculate / measure the extension

Hazard 1: Clamp (stand, boss and masses) might fall off desk

Risk: injury to feet

Precaution: Use clamp to fix apparatus to the bench or ensure that the slotted masses hang over the base/foot of the stand or ensure that the boss is screwed tightly into the stand and clamp or put (heavy) masses on the base/foot of the stand or stand up so that you can move out of the way

Hazard 2: Spring could break/come loose

Risk: damage eye

Precaution: Wear safety goggles

If a risk assessment/possible hazard was not given, the answer could still reach level 3, but full marks would not be awarded.

Full marks may be awarded for alternative feasible methods.

[6 marks]

(Total 17 marks)