GCSE Physics Required Practical: Investigating Newton's Second Law

Key Stage 4

Meaning

Investigate the relationship between the force and acceleration of an object.

Experiment 1a: Light Gates Measuring Time and Velocity

Variables

Independent Variable: The force applied to the object.

Dependent Variable: The acceleration of the object.

Control Variables: The mass of the object.

Method

A diagram of the apparatus used to investigate the effect of a force on the acceleration of an object.

Set up the equipment as shown in the diagram.

1. Program into the light gates the length of the card on the glider as 2cm.
2. Set the light gates to record the velocity through the gate and the time taken to travel between gates.
3. Attach a known weight (approximately 0.1N) to wire.
4. Release the weight and allow the glider to accelerate.
5. Record the velocity through light gates 1 and 2 and the time taken between light gates.
6. Use the equation \(a=\frac{v-u}{t}\) to calculate the acceleration of the glider.
7. Repeat steps 3-6 adding 0.1N weight up to around 0.6N.
8. Plot a scatter graph with the force of weight on the x-axis and the acceleration on the y-axis. The gradient of line of best fit will be the mass of the glider showing that \(F=ma\).
9. Measure the mass of the glider using an electronic balance to compare results.

Improving Accuracy

Calculate the weight added by measuring its mass using an electronic balance on a flat, level surface each time and using the equation \(W=mg\) with \(g=9.8\). This will give a more accurate knowledge of the weight rather than relying on the number printed on the weights.

Ensure the glider remains motionless when no weight is attached. If the glider moves then adjust the feet on the air track until the glider remains stationary.

Lubricate the pulley to reduce the force of friction which acts against the weight added.

Experiment 1b: Light Gates Measuring Displacement and Velocity

Variables

Independent Variable: The force applied to the object.

Dependent Variable: The acceleration of the object.

Control Variables: The mass of the object.

Method

A diagram of the apparatus used to investigate the effect of a force on the acceleration of an object.

Set up the equipment as shown in the diagram.

1. Program into the light gates the length of the card on the glider as 2cm.
2. Set the light gates to record the velocity through the gate.
3. Measure and record the distance between the light gates using a ruler. This will be the displacement of the glider.
4. Attach a known weight (approximately 0.1N) to wire.
5. Release the weight and allow the glider to accelerate.
6. Record the velocity through light gates 1 and 2.
7. Use the equation \(v^2 - u^2=2as\) to calculate the acceleration of the glider.
8. Repeat steps 4-7 adding 0.1N weight up to around 0.6N.
9. Plot a scatter graph with the force of weight on the x-axis and the acceleration on the y-axis. The gradient of line of best fit will be the mass of the glider showing that \(F=ma\).
10. Measure the mass of the glider using an electronic balance to compare results.

Improving Accuracy

Calculate the weight added by measuring its mass using an electronic balance on a flat, level surface each time and using the equation \(W=mg\) with \(g=9.8\). This will give a more accurate knowledge of the weight rather than relying on the number printed on the weights.

Ensure the glider remains motionless when no weight is attached. If the glider moves then adjust the feet on the air track until the glider remains stationary.

Lubricate the pulley to reduce the force of friction which acts against the weight added.

Improving Precision

Use a ruler with a higher resolution to give a more precise displacement for the glider.

Experiment 2: Trolley with Markings

Variables

Independent Variable: The force applied to the object.

Dependent Variable: The acceleration of the object.

Control Variables: The mass of the object.

Method

A diagram of the apparatus used to investigate the effect of a force on the acceleration of an object.

Set up the equipment as shown in the diagram.

1. Adjust the gradient of the slope so that once pushed the trolley will move with a constant velocity.
2. Attach a known weight (approximately 0.1N) to wire.
3. Release the weight and start the stopwatch allowing the trolley to accelerate.
4. Record the time on the stopwatch at each 10cm marker.
5. Calculate the time difference between each 10cm marker.
6. Use the equation \(v=s/t\) to calculate the average velocity between each 10cm marker.
7. Use the equation \(a=\frac{v-u}{t}\) to calculate the acceleration of the trolley.
8. Repeat steps 2-7 adding 0.1N weight up to around 0.6N.
9. Plot a scatter graph with the force of weight on the x-axis and the acceleration on the y-axis. The gradient of line of best fit will be the mass of the glider showing that \(F=ma\).
10. Measure the mass of the trolley using an electronic balance to compare results.

Improving Accuracy

Calculate the weight added by measuring its mass using an electronic balance on a flat, level surface each time and using the equation \(W=mg\) with \(g=9.8\). This will give a more accurate knowledge of the weight rather than relying on the number printed on the weights.

Adjust the friction compensated slope so that the trolley will move at constant velocity when no unbalanced force is applied.

Lubricate the pulley to reduce the force of friction which acts against the weight added.

Use light gates and a data logger to record the time taken between each marker.

Use a smaller weight so that the trolley moves more slowly allowing the timing to be more accurate.

Improving Precision

Use light gates and a data logger to record the time taken between each marker to reduce the random error caused by the human use of a stopwatch.