AQA GCSE Physics Physics Paper 2 (Foundation), June 2025: Question 7

✅ Correct Answer

Tick the 3rd box:

The turning effect of the force

💡 Key Knowledge

A moment is defined in physics as the turning effect of a force about a pivot or rotational axis.

❌ Common Errors

• Confusing "moment" with "momentum" (which relates to mass and velocity).
• Selecting "the magnitude of the force" — magnitude simply means the size in Newtons, not its turning capability.

🧠 Exam Technique

Whenever you see "moment of a force" at GCSE, instantly associate it with the phrase turning effect.

✅ Correct Answer

Tick the 2nd box:

The resultant moment is clockwise.

💡 Key Knowledge

The beam was originally balanced (equilibrium). Adding a tag on peg 7 to the right creates an unbalanced downward pull on the right-hand side, causing the beam to tip downwards on the right (a clockwise rotation).

🧠 Visualising Direction

Imagine the hands of a clock pinned at the pivot:

• Downward force to the right of pivot = Clockwise ⟳
• Downward force to the left of pivot = Anti-clockwise ⟲

❌ Common Errors

Thinking the resultant moment is zero because the student was holding it. The question asks what happens when the student lets go of the beam.

✅ Correct Answer

• Place the tag to the left of the pivot [1 mark]
• On position 7 (peg 7) [1 mark]

💡 Key Knowledge: Principle of Moments

For an object in equilibrium (balanced):

Total Clockwise Moment = Total Anti-clockwise Moment

Since each tag has the identical weight ( W ), to balance an extra tag added at distance 7 to the right, you must place an equal tag at distance 7 on the left:
W × 7 = W × 7 .

🧠 Exam Technique

This is a 2-mark question asking "where" to put the tag. You need two pieces of information:

1. Side: left of the pivot.
2. Specific location: peg / position 7.

❌ Common Errors

Only stating "position 7" without stating that it must go on the left side, losing 1 of the 2 marks.

✅ Correct Answer

moment = force × distance

or

M = F d  (or M = F × d )

💡 Key Knowledge

Full definition: Moment is the force multiplied by the perpendicular distance from the pivot to the line of action of the force.

Standard units: Force in Newtons ( N ), Distance in metres ( m ) or centimetres ( cm ), Moment in N m or N cm .

❌ Common Errors & Unit Traps

• Unit panic: Students often try to convert cm to metres unnecessarily. Here, the moment is already in N cm and the question requests the answer in cm, so no unit conversion is required!
• Inverting the division: Calculating 0.15 / 1.8 = 0.083 instead of 1.8 / 0.15 . Always check that distance = moment ÷ force.

🧠 Exam Technique

Always show your substitution before rearranging. If you miscalculate the arithmetic, you still secure the substitution mark.