Required Practical - Effects on Acceleration

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Investigating How Force Affects Acceleration

This practical explores Newton’s Second Law of Motion – to determine how the acceleration of an object varies when the force acting on it is changed (keeping mass constant).

Apparatus

Air track and air blower (to minimise friction)
Air track glider
Bench pulley
String
Slotted masses (e.g. 20g, 30g, 40g)
Two light gates
Ruler (for distance and card length)
Interrupt card (attached to glider, known length such as 0.10 m)

Method

Set up the air track on a level bench with a pulley at one end.
Connect the glider to a hanging mass using a light string that runs over the pulley.
Attach an interrupt card to the glider so it passes through both light gates before the hanging mass reaches the floor.
Ensure the air track is switched on to create an air cushion that reduces friction.
Add a total hanging mass of 100 g.
Release the glider and record the acceleration shown by the data logging software.

Method (continuation)

Repeat the test twice more and calculate a mean acceleration.
Reduce the hanging mass each time (e.g. to 80 g, 60 g, 40 g, and 20 g) and repeat the process for each value of force.
Record all force and acceleration values.

Analysis

Plot a graph of acceleration (y-axis) against force (x-axis).
Draw a line of best fit through your data points.
If the results are accurate, the line should pass through the origin and show a directly proportional relationship.
- As force increases, acceleration increases at a constant rate.
Check if the results support Newton’s Second Law:
- $F=m$$ x $$a$

Safety Precautions

Faulty wiring may cause electric shock or fire – Inspect cables and plugs for damage before switching on.
Falling masses or glider could cause bruising or foot injury, so use small masses or stand back once the glider is released.

Investigating How Mass Affects Acceleration

This experiment explores Newton’s Second Law, focusing on how the acceleration of an object changes when its mass varies but the applied force remains constant.

Apparatus

Air track and blower (to reduce friction)
Glider with an interrupt card
Pulley and light string
Slotted masses
Two light gates and data logging software
Ruler or digital scale for measuring
Power supply for air track

Method

Set up the air track on a flat surface, with a pulley at one end.
Attach the glider to a hanging mass using a string.
Keep the pulling force constant (e.g. use a hanging mass of 100 g).
Begin with the glider’s base mass and add slotted masses one by one to increase its total mass.

Method (continuation)

For each trial:
- Release the glider from rest.
- Measure its acceleration using two light gates connected to a data logger.
- Record the total mass (glider + added masses) and acceleration.
Repeat each run twice more to obtain a reliable mean acceleration value.

Analysis

Convert all measured masses to kilograms (kg).
For each test, calculate the reciprocal of mass (1/m).
- Example: For a mass of 0.1 kg, 1/m = 10 kg^-1
Plot a graph of acceleration (y-axis) against 1/mass (x-axis).
Draw a line of best fit and interpret the pattern.

Evaluation

As the total mass decreases (so 1/m increases), the acceleration should increase.
A direct proportional relationship between acceleration and 1/mass supports Newton’s Second Law.
Ideally, the graph should form a straight line through the origin.
Check whether your data supports the predicted relationship.
Identify and discuss any anomalous results.

Safety Precautions

Ensure power cables are not frayed or exposed to avoid electrical shock or fire.
Falling masses or glider could cause bruising or foot injury – Use small masses or stand back once the glider is released.