Investigating Acceleration
Learn Investigating Acceleration for GCSE Physics with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA, Edexcel and OCR. Investigate how the acceleration of a trolley depends on the force applied to it and on its mass.
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These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA, Edexcel and OCR specifications. Every worksheet comes with a full mark scheme.
Topic overview
This required practical investigates how acceleration is affected by the force applied and by the mass of the object.
A trolley is placed on a track and connected by a string over a pulley to a hanging mass, which provides the accelerating force. Light gates measure the velocity at two points, allowing the acceleration to be calculated.
To investigate force, the total mass of the system is kept constant by moving masses from the trolley to the hanger rather than adding new ones. To investigate mass, the hanging mass is kept constant while masses are added to the trolley. Keeping the total mass constant in the first investigation is the point students most often miss.
Revision notes
The apparatus
A trolley on a track is connected by a string over a pulley to a hanging mass.
The weight of the hanging mass provides the accelerating force. Light gates measure the velocity at two points so the acceleration can be calculated.
Investigating force
Vary the accelerating force by moving masses from the trolley to the hanger.
Crucially, this keeps the total mass of the system constant — the masses are transferred, not added. Adding new masses would change both variables at once.
Investigating mass
Keep the hanging mass, and therefore the accelerating force, constant.
Add masses to the trolley to increase the total mass of the system. Acceleration should decrease as mass increases, confirming the inverse proportionality.
Key points
- A hanging mass provides the accelerating force.
- Light gates measure velocity to find acceleration.
- Move masses from trolley to hanger to vary force.
- This keeps the total mass constant.
- Add masses to the trolley to vary mass.
- Keep the hanging mass constant when varying mass.
Worked examples
Example 1
Explain why masses are moved from the trolley to the hanger rather than being added. [3 marks]
Model answer
Moving the masses keeps the total mass of the system constant (1 mark). Adding new masses would change both the accelerating force and the total mass at the same time (1 mark), so it would be impossible to tell which was causing the change in acceleration (1 mark).
Example 2
State the variable that must be kept constant when investigating the effect of mass on acceleration. [2 marks]
Model answer
The accelerating force must be kept constant (1 mark), which is achieved by keeping the hanging mass unchanged (1 mark).
Example 3
Describe how light gates are used to find the acceleration of the trolley. [2 marks]
Model answer
The light gates measure the velocity of the trolley at two points along the track (1 mark), and the acceleration is calculated from the change in velocity divided by the time between them (1 mark).
Common mistakes
Adding masses to the hanger instead of moving them.
This changes the total mass as well as the force, so the test is not fair.
Varying both force and mass together.
Only one variable should change at a time.
Forgetting friction.
The track may need compensating for friction, or friction should be acknowledged as a source of error.
Measuring only one velocity.
Two velocities are needed to calculate the change and hence the acceleration.
Exam tips
- Explain the mass-transfer method clearly — it is the key point.
- Name the control variable for each investigation.
- Describe how light gates give acceleration.
- Mention friction as a source of error.
Key terms
- Light gate
- A device measuring velocity as an object passes.
- Accelerating force
- The force causing the trolley to accelerate.
- Control variable
- A variable kept constant for a fair test.
- Total mass
- The mass of the trolley plus the hanging masses.
Related topics
Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.