AQA GCSE Combined Science: Trilogy Physics Paper 2 (Higher), 2018: Question 1

💡 Key knowledge

• Acceleration happens when there is a resultant force.
• For a fixed force, increasing mass reduces acceleration.
• For a fixed mass, increasing resultant force increases acceleration.
• Repeated measurements are used to calculate a mean and identify anomalies.

🧠 Exam technique

• Use the exact trend stated in the question data.
• For calculations, show how the mean is found.
• When a result is odd, say it is anomalous and explain what to do with it.

❌ Common errors

• Mixing up resultant force and acceleration.
• Giving a long explanation instead of the one mark trend statement.
• Not spotting that 1.26667 and 6.7 are not acceptable mean values.

✅ Correct answers

Tick:

• Its acceleration would decrease to zero.
• The resultant force on it would decrease to zero.

2 marks: 1 mark for each correct tick.

💡 Key knowledge

When the hanging mass reaches the ground, it no longer pulls the glider forward. With no pulling force, the resultant force becomes zero, so the glider’s acceleration becomes zero.

❌ Common errors

• Ticking “its speed would increase” — speed will not keep increasing if the force is gone.
• Saying the force “stops” without linking it to the resultant force becoming zero.

✅ Correct answer

Move the second light gate closer to the first.

Also accepted: shorten the string length, or use a taller table.

1 mark for any one valid method.

🧠 Exam technique

The examiner wants a practical change that gives the glider less distance to travel before it reaches the second gate or the ground.

❌ Common errors

• Changing the air track or light gates in a vague way without saying how.
• Saying “slow the glider down” — the mark scheme wants a setup change.

📐 Calculations: how to check a mean

1. Add the three test values.
2. Divide by 3.
3. Check if the answer is given to 2 significant figures or 1 decimal place.

Example 0.20 N: (1.3 + 1.2 + 1.3) ÷ 3 = 1.26667...
Correct mean = 1.3 m/s² (to 2 s.f. or 1 d.p.).

Example 0.98 N: 6.4, 7.2, 6.4 includes an anomalous result.
Discard the anomaly and recalculate: (6.4 + 6.4) ÷ 2 = 6.4 m/s².

✅ Correct answers

Mistake 1: 1.26667 m/s² is wrong because it is not rounded.

Correction: give the value to 2 significant figures or 1 decimal place → 1.3 m/s².

Mistake 2: 6.7 m/s² is wrong because the anomalous result has not been dealt with.

Correction: discard the anomalous result and recalculate the mean → 6.4 m/s².

4 marks: 1 mark for each mistake, 1 mark for each correct correction.

💡 Key knowledge

• An anomalous result does not fit the pattern.
• Good practice is to repeat it and then calculate a new mean.
• Means should be reported using sensible rounding.

❌ Common calculation traps

• Leaving the mean as 1.26667 .
• Using the wrong number of values after removing the anomaly.
• Writing 6.7 because you included the odd result.
• Forgetting units: always use m/s².

✅ Correct answer

The resultant force is directly proportional to acceleration.

Acceptable alternative: the larger the resultant force, the greater the acceleration.

1 mark for a correct conclusion from Table 1.

💡 Key knowledge

From the table, as resultant force increases from 0.20 N to 0.98 N, the acceleration increases from about 1.3 m/s² to about 6.4 m/s². This shows a clear positive relationship.

🧠 Exam technique

For a conclusion, do not just repeat raw numbers. State the pattern in words, using scientific language such as directly proportional or positive correlation.

📐 What the graph should show

1. Plot all five points correctly on the axes.
2. Use small, neat crosses.
3. Draw a curved line of best fit, not a straight line.

Points to plot:

• (0.060, 3.5)
• (0.080, 2.6)
• (0.10, 2.0)
• (0.12, 1.7)
• (0.14, 1.4)

✅ Mark scheme focus

2 marks for plotting all points accurately within ½ small square.

1 mark for a curved line of best fit.

Even if a small plotting error happens, you can still gain some marks if most points are correct.

❌ Common errors

• Drawing a straight line instead of a curve.
• Swapping the axes around.
• Using a ruler to join the points exactly.
• Not matching the decreasing trend as mass increases.

✅ Correct answer

Inversely proportional.

Also accepted: as mass increases, acceleration decreases.

1 mark for the relationship statement.

💡 Key knowledge

At constant resultant force, a larger mass means a smaller acceleration. This fits Newton’s second law: F = ma.

❌ Common errors

• Saying “directly proportional” — that is the opposite trend.
• Only describing one point instead of the full relationship.

💡 Remember

• Acceleration depends on resultant force and mass.
• Means must be rounded properly.
• Anomalies should be identified and ignored in the final mean.
• Use the exact trend word: directly proportional or inversely proportional.

🧠 How marks are awarded

• 1-mark questions need one clear correct statement.
• Calculation questions reward method and final rounded answer.
• Graph questions reward both plotting and line shape.