AQA GCSE Combined Science: Trilogy Physics Paper 2 (Higher), 2020: Question 3

✅ Correct answer

The spring will return to its original length when the force is removed.

1 mark for selecting the statement that describes elastic behaviour.

💡 Key knowledge

• Elastic means an object returns to its original shape or length after the force is removed.
• A spring can be stretched or compressed and still be elastic, as long as it returns to its starting length.

🧠 Exam technique

• Look for the idea of returning to original length.
• Do not choose answers that only say the spring changes shape — that is too vague.

❌ Common errors

• Choosing “the spring will become deformed” is wrong because it does not say it recovers.
• Choosing “the spring will become longer when the force is removed” is the opposite of elastic behaviour.

✅ Correct answers

• spring constant
• (original) length
• diameter

Any two of these gained the 2 marks.

💡 Key knowledge

If the springs are meant to behave the same way in the keyboard, they need matching physical properties. The mark scheme accepted:

• same spring constant — so they need the same force for the same extension
• same original length
• same diameter

🧠 Exam technique

• You only need two properties.
• Write clear, science-based terms: for example, “diameter” is better than “size”.
• Marks are for matching the mark scheme idea, not for explaining in detail.

❌ Common errors

• Writing “same force” or “same pressure” — these are not properties of the spring itself.
• Giving only one property.
• Using vague words like “same shape” without a specific measurable property.

📐 Calculation steps

1. Use Hooke’s law: F = kx
2. Substitute the values: 0.80 = k × 0.0040
3. Rearrange: k = 0.80 ÷ 0.0040
4. Calculate: k = 200
5. State the unit: N/m

Spring constant = 200 N/m

✅ Correct answer

200 N/m

3 marks were available: one for the correct equation, one for rearranging, and one for the final answer with unit.

💡 Key knowledge

• Hooke’s law: force is proportional to extension, so F = kx .
• k is the spring constant.
• Extension must be in metres, not cm or mm.

🧠 Exam technique

• Always include the equation before substituting values — this is often where the first mark is earned.
• Check units carefully: N/m is required.
• Use the numbers exactly as given: 0.80 N and 0.0040 m.

❌ Common errors

• Using k = F + x or dividing in the wrong order.
• Forgetting to convert the extension into metres.
• Writing the answer without units.
• Using 0.04 m instead of 0.0040 m .

✅ Correct answers

• The upward force on the spring is equal to the downward force.
• The spring is inelastically deformed.

These two statements match the mark scheme exactly.

💡 Key knowledge

• If the spring is stationary, the forces are balanced: upward force = downward force.
• Beyond the limit of proportionality, extension is no longer directly proportional to force.
• If the spring has been stretched beyond this point, it is inelastically deformed and may not return to its original shape.

🧠 Exam technique

• Use the clue stationary — this tells you the forces must balance.
• Do not confuse limit of proportionality with breaking point.
• Pick statements that describe both the forces and the condition of the spring.

❌ Common errors

• “The extension is directly proportional to the force applied” is false because the spring is beyond the limit of proportionality.
• “The spring cannot be stretched any further” is not guaranteed by the information given.
• “The elastic potential energy of the spring is zero” is wrong because the spring is stretched.

✅ 03.1

The spring will return to its original length when the force is removed.

✅ 03.2

Any two: spring constant, original length, diameter.

✅ 03.3

0.80 = k × 0.0040 → k = 200 N/m

✅ 03.4

Upward force = downward force; spring is inelastically deformed.