AQA AS Level Physics Paper 2, June 2023: Question 33
1 mark · Medium difficulty · Multiple Choice
Calculate the average resistive force acting on a pellet of mass 25 g travelling horizontally at 40 m s^-1 that stops after travelling a horizontal distance of 2.5 cm in a wooden block.
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Question text
33 A pellet of mass 25 g travelling horizontally at 40 m s−1 enters a fixed wooden block. The
pellet stops after travelling a horizontal distance of 2.5 cm in the block.
What is the average resistive force acting on the pellet?
[1 mark]
A 20 N
B 800 N
C 1600 N
D 8000 N
Mark scheme
Show the mark scheme
33 B 800 N
How to answer it
Calculating Average Resistive Force in Stopping Problems
This question assesses your ability to apply the work-energy principle (or kinematic equations of motion) to find an average resistive force. You must expertly handle unit conversions (grams to kilograms, centimetres to metres) and correctly rearrange equations under strict timed conditions.
Question 3.3
Multiple Choice: Finding the Average Resistive Force
✅ Correct Answer
Option B: 800 N
💡 Key Knowledge
- Work-Energy Principle: Work done by the resistive force equals the initial kinetic energy of the pellet ( F × d = 0.5 × m × v² ).
- Alternative Approach: Kinematic equations ( v² = u² + 2as ) combined with Newton's Second Law ( F = ma ).
🧠 Exam Technique
- Always convert prefixes to SI base units before plugging numbers into your calculator.
- Look out for common distractor answers generated by forgetting unit conversions (e.g., omitting the 10⁻³ or 10⁻² factors).
❌ Common Errors
- Forgetting to convert 25 g into kg ( 25 × 10⁻³ kg ).
- Forgetting to convert 2.5 cm into m ( 2.5 × 10⁻² m ).
- Failing to square the velocity term ( v² ).
📐 Step-by-Step Calculation
- Identify given values in standard units: Mass m = 25 g = 0.025 kg , Initial velocity u = 40 m s⁻¹ , Final velocity v = 0 m s⁻¹ , Distance d = 2.5 cm = 0.025 m .
- Set up the Work-Energy equation: Work Done = Kinetic Energy Lost
F × d = 0.5 × m × u² - Rearrange for Force (F): F = (0.5 × m × u²) / d
- Substitute the values: F = (0.5 × 0.025 × 40²) / 0.025
- Simplify and solve: Notice that the 0.025 term cancels out!
F = 0.5 × 40² = 0.5 × 1600 = 800 N .
Topics
Physics · 3.4 Mechanics and materials
Question and mark scheme from the AQA AS Level Physics examination, Paper 2, June 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.