Study Hack Lab

RP 7Physics

Acceleration

Write-up template

Name
Date
Course: GCSE Physics
Board and specification: AQA GCSE Physics (8463), 4.5.6.2.2AQA GCSE Combined Science: Trilogy (8464), 6.5.4.2.2Apparatus and techniques: AT 1, AT 2, AT 3
Class and teacher

Aim

Investigate how the acceleration of a trolley depends on the resultant force on it (mass constant) and on its mass (force constant).

Plan and risk assessment
Apparatus
Method
Results
Graph
Analysis
Conclusion and evaluation
Make safe and clear up

A blank write-up for use in a real lesson. The headings follow the AQA required practical; the readings are yours to take. Layout v1, practical v2. Original material; not affiliated with AQA, which has not reviewed it.

1 Plan and risk assessment

A resultant force makes a mass accelerate: resultant force = mass × acceleration. Double the force on the same mass and the acceleration doubles; double the mass with the same force and it halves. The hanging weight provides the pull; the resultant force also accounts for friction and the runway slope. The mass is everything the string accelerates: the trolley, the hanger and every mass on either.

F = m a

Variables

Independent (you change)
Dependent (you measure)
Control (you keep the same)

Prediction

Keeping the total mass the same, you double the force pulling the trolley. What happens to its acceleration?

Keeping the force the same, you double the mass being accelerated. What happens to the acceleration?

With friction compensated, what will your graph of acceleration against force look like?

Risk assessment

Hazard	Harm it could cause	Control

2 Apparatus

Dynamics trolley The object being accelerated.
10 cm card on the trolley Cuts the light gate beams.
Runway (1.3 m) A smooth, straight track for the trolley.
Wooden block Tilts the runway to compensate for friction.
Bench pulley and clamp Turns the hanging weight into a horizontal pull.
String Joins the trolley to the mass hanger.
20 g mass hanger and four 20 g slotted masses Their weight is the accelerating force (0.2–1.0 N).
Four 200 g trolley masses Change the mass of the trolley in part 2.
Two light gates and a data logger (resolution 0.01 m/s²) Measure the speed at each gate and the acceleration.
Stopwatch (resolution 0.01 s) The other way to time the trolley.
Metre rule (resolution 1 mm) Measures the card and the distances along the runway.
Digital balance (resolution 0.1 g) Measures the mass of the trolley.
Box of sand and an end stop Catch the falling masses and the trolley.

3 Method

Write numbered steps someone else could follow. Say what you measure, with which instrument, and how you keep it a fair test.

4 Results

The table is drawn before you measure. Record each reading to the resolution of the instrument, then work out the mean of your repeats, leaving out any anomaly.

The trolley

Mass of the trolley in g

Part 1: changing the force (total mass constant) · The logger shows the acceleration for each run. Force = weight of the hanging masses, W = m g (g = 9.8 N/kg).

Mass on the hanger in g	Force in N	Total moving mass in kg	Trial 1 in m/s²	Trial 2 in m/s²	Trial 3 in m/s²	Mean acceleration in m/s²
20
40
60
80
100

Part 2: changing the mass (100 g on the hanger) · Total mass = trolley + masses added + the hanger and its four masses (100 g). The first row is your 100 g run from part 1.

Mass added to the trolley in g	Total mass in kg	1 ÷ total mass in 1/kg	Trial 1 in m/s²	Trial 2 in m/s²	Trial 3 in m/s²	Mean acceleration in m/s²
0
200
400
600
800

Anomalies

Ring any anomalous result. Say what probably went wrong and whether you repeated it.

5 Graph

Acceleration against force (mass from gradient) · Choose your axes: the independent variable goes on the x-axis. Label each axis with the quantity and unit.

Acceleration against 1 ÷ mass · Choose your axes: the independent variable goes on the x-axis. Label each axis with the quantity and unit.

6 Analysis

The force with 60 g on the hanger
weight = mass × gravitational field strength (W = m g)
Answer
The acceleration with 100 g on the hanger
acceleration = change in velocity ÷ time taken (a = Δv ÷ t)
Answer
Mass estimate (1 ÷ gradient, constant-mass model)
Answer
Where did the pull go?
Answer
1 ÷ mass
total mass = trolley + masses added + hanger and its masses (0.100 kg)
Answer
Gradient (the accelerating force)
Answer

7 Conclusion and evaluation

Conclusion

Conclusion: what do your results show? Use your own numbers.

Sources of error

For each, say whether it is systematic or random, and how it affected your results.

Friction not compensated (runway flat or not tilted enough)

Total mass not kept constant (new masses added to the hanger from the box)

Reaction time starting and stopping a stopwatch

Second light gate (or finish line) after the point where the hanger lands

Card length typed into the logger not measured

Small differences from run to run (wheels, string, how the trolley is let go)

Improvement

How could you improve the method? Say why it would help.

8 Make safe and clear up

Lift the masses off the hanger and the trolley and put them back in the box
Switch off the data logger and unplug the light gates
Untie the string, unclamp the pulley and put the box of sand away
Take the block from under the runway and put the trolley away