Question 1 (2 marks)
Knowledge
State Newton’s second law in equation form.
Show model answer / marking points
F = ma (1) with F resultant force, m mass and a acceleration (1).
Required Practical 19: Acceleration | AQA GCSE Science | The Science Department
About this practical and its aim
Aim
Investigate how force and mass affect acceleration of an object.
Introduction
You will, by now, know about Newton's laws of motion. Here you get to see them in action and draw your own conclusion about the relationships between mass, force and acceleration. When you are calculating the results, make sure that you observe everything you can including how the masses are applying the force, the friction of the car's tyres/wheels and even if the toy cars have the same amount of drag at the same speed.
The science behind the practical
Newton’s second law predicts F = ma, so acceleration increases with force at constant mass and decreases as mass increases for constant force.
Key things to remember
Measure acceleration with gates or motion sensor; conduct separate force and mass investigations.
Equipment and apparatus
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Dynamics trolley
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runway/track
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pulley and string
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mass hanger and masses
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light gates or motion sensor
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data logger
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balance
Method: How to carry out the experiment
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Collect the equipment to setup the apparatus as shown in the diagram
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Mark the table every 20cm for the final 1m from the edge of the bench
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Add 10g mass to the end of the string (approximate the 10g to 0.1N)
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Release the masses and start a stop clock at the same time
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Record the time taken to reach every marker (20cm, 40cm, 60cm, 80cm and 100cm). You may have to repeat this in order for your team to catch all of these
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Repeat the experiment and add 10g each time until you have 100g (approximate 100g to 1N)
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Results - you now need to work out the average velocity of your car for each 20 cm. This is worked out as distance (0.2 M)/time taken (time difference between markers in seconds).
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You can now work out the accelerations. The changes in velocities / time taken
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Now compare the relationship between acceleration and force applied.
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Extension - you can further investigate F=ma by keeping the force on the car the same and varying the mass of the car. Keep the number of masses pulling the car constant and add masses to the roof of the car and measure its effect
Variables and fair testing
| Type of variable | What is measured or controlled? |
|---|---|
| Independent variable | Resultant force or total moving mass |
| Dependent variable | Acceleration (m/s²) |
| Control variables | Track slope; friction; method of release; force or mass held constant in each investigation |
Safety and managing risks
Follow your teacher's instructions and your school's risk assessment. This page is not a substitute for a formal risk assessment.
| Hazard | Risk | Precaution |
|---|---|---|
Moving trolley and falling masses |
Impact or dropped weights |
Use a clear runout area and catch falling masses safely. |
Trailing cables/track |
Trips |
Secure track and keep floor area clear. |
Results, calculations and analysis
Recording, presenting and interpreting results
Tables: force (N), mass (kg), acceleration (m/s²). Plot acceleration against force and acceleration against reciprocal of mass where suitable.
Calculations
Acceleration = change in velocity ÷ time; F = ma.
Conclusions, accuracy and evaluation
Drawing a conclusion
Acceleration is proportional to resultant force for constant mass and inversely proportional to mass for constant force.
Evaluating the investigation
Correct for friction, check the total moving mass and repeat measurements with consistent release.
More to learn
Keeping mass constant
In a pulley-trolley setup, moving masses between trolley and hanger can alter driving force while keeping total mass approximately constant.
Common exam mistake
Acceleration depends on resultant force, not simply a pulling force if friction is significant.
GCSE examination practice
Answer each question in full before opening the model answer. Check your work against the marking points and look for scientific key words.
Question 2 (2 marks)
Calculation
Resultant force is 2.4 N on a mass of 0.80 kg. Calculate acceleration.
Show model answer / marking points
a = F/m = 2.4 ÷ 0.80 = 3.0 m/s² (2).
Question 3 (2 marks)
Variables
When investigating force, what must be held constant?
Show model answer / marking points
Total moving mass (1); other conditions such as track friction/slope also consistent (1).
Question 4 (2 marks)
Evaluation
Suggest one improvement to make the investigation more reliable and explain why it helps.
Show model answer / marking points
Repeat measurements and calculate a mean (1), reducing the influence of random variation/anomalies (1). Alternative valid improvement specific to the experiment with explanation can gain both marks.
This page was updated on: 25th June 2026