AQA GCSE Physics Physics Paper 1 (Higher), November 2020: Question 6
10 marks · Standard Demand difficulty · Short Answer
Calculate the mass of a rider from gravitational potential energy change and vertical height, and explain why riders have similar speeds at the bottom of a water slide.
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Question text
06 Figure 9 shows a theme park ride called AquaShute.
Riders of the AquaShute sit on a sled and move down a slide.
Figure 9
06.1 A light gate and data logger can be used to determine the speed of each rider and
sled.
What two measurements are needed to determine the speed of a rider and sled?
[2 marks]
Tick ( ) two boxes.
Gravitational field strength
Length of sled
Mass of rider and sled
Temperature of surroundings
Time for sled to pass light gate 21
06.2 The decrease in gravitational potential energy of one rider on the slide was 8.33 kJ.
*20* The rider moved through a vertical height of 17.0 m.
gravitational field strength = 9.8 N/kg
Calculate the mass of the rider.
[4 marks]
Mass of rider = kg
06.3 At the bottom of the slide, all riders and their sleds have approximately the same
speed.
Explain why.
[4 marks]
Mark scheme
Show the mark scheme
Question 6
AO /
Question Answers Extra information Mark
Spec. Ref.
06.1 Length of sled 1 AO2
4.1.1.2
Time for sled to pass light gate 1
06.2 AO2
Ep = 8330 (J) 1 4.1.1.2
8330 = m × 9.8 × 17.0 allow a correct substitution using 1
an incorrectly/not converted
value of Ep
8330 allow a correct rearrangement 1
m = using an incorrectly/not
9.8 ×17.0
converted value of Ep
m = 50.0 (kg) allow a correct calculation using 1
an incorrectly/not converted
value of Ep
06.3 ½ mv2 = mgh 1 AO1
or 4.1.1.2
decrease in Ep = increase in Ek
masses cancel on both sides of 1
the equation
or
v2 = 2gh
(final) speed only depends on 1
vertical height (and gravitational
field strength)
variations will be due to air 1
resistance/friction
or
different initial speed
Total 10
How to answer it
Energy Changes & Speed on a Theme Park Ride
What this question tests
This question assesses your understanding of energy stores, the conservation of energy, and practical methods for measuring speed in the laboratory or field. You will need to recall and apply equations for gravitational potential energy ( E_p = mgh ) and kinetic energy ( E_k = 0.5mv² ), rearrange formulas, convert metric units (kilojoules to joules), and explain physical principles logically.
Measuring Speed with a Light Gate
What two measurements are needed to determine the speed of a rider and sled?
✅ Correct Answers (Tick Two)
- Length of sled
- Time for sled to pass light gate
💡 Key Knowledge
Speed is calculated using the formula speed = distance / time . As the sled breaks the infrared beam of a light gate, the "distance" is the physical length of the moving object (the sled), and the "time" is how long the light beam is blocked.
❌ Common Errors
Students often incorrectly select "Mass of rider and sled" or "Gravitational field strength", confusing variables needed for energy calculations with the kinematic definition of speed.
Calculating Mass from Gravitational Potential Energy
The decrease in E_p of one rider was 8.33 kJ, vertical height was 17.0 m, and g = 9.8 N/kg. Calculate the mass.
📐 Step-by-Step Calculation
- Convert units: Convert kilojoules to joules.
8.33 kJ = 8330 J (Multiply by 1000). - State the equation:
E_p = m × g × h - Substitute values:
8330 = m × 9.8 × 17.0 - Rearrange and solve:
m = 8330 / (9.8 × 17.0)
m = 8330 / 166.6 = 50.0 kg
❌ Common Calculation Traps
- Unit Neglect: Forgetting to convert 8.33 kJ into 8330 J results in a mass calculation that is off by a factor of a thousand!
- Significant Figures: The data is given to 3 significant figures, so your final answer should ideally match ( 50.0 kg ).
🧠 Exam Technique
Always write out the un-rearranged formula first, even if you are confident with algebra. Examiners award method marks for correct substitution even if a minor arithmetic error occurs later in the calculation.
Explaining Equal Speeds
At the bottom of the slide, all riders and sleds have approximately the same speed. Explain why.
✅ Marking Points Required
- State energy conservation: Loss in E_p = Gain in E_k (or mgh = 0.5mv² ).
- Explain that mass ( m ) appears on both sides and cancels out.
- Derive or state that final speed depends only on vertical height ( h ) and gravitational field strength ( g ).
- Acknowledge real-world factors: Variations in speed are due to friction/air resistance or different starting speeds.
💡 Key Physics Principle
By equating gravitational potential energy to kinetic energy:
mgh = 0.5mv²
Dividing both sides by mass leaves:
gh = 0.5v² , which rearranges to v = √(2gh) . Notice mass ( m ) has completely disappeared from the formula!
🧠 Examiner Commentary
Higher-tier candidates instantly recognised the algebraic cancellation of mass. To secure full marks, students must also mention why speeds aren't completely identical in reality—referencing non-conservative forces like air resistance, friction with the water, or differing initial pushes at the top.
Topics
Physics · P1: Energy
Question and mark scheme from the AQA GCSE Physics examination, Physics Paper 1 (Higher), November 2020. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.