# Required practical

## Investigating force and acceleration

There are different ways to investigate the effect of varying the force on an object. In this required practical activity, it is important to:

• make and record measurements of length, mass and time accurately
• measure and observe the effect of force
• use appropriate apparatus and methods to measure motion

The diagram shows apparatus that can be used in this investigation. A constant stream of air reduces the friction between the glider and the air track.

### Aim of the experiment

To investigate the effect of varying the force on the acceleration of an object.

### Method

1. Position an air track on a bench with a bench pulley at one end and two light gates above the track. Cut an interrupt card to a known length (such as 10 cm) and attach it to an air track glider.
2. Connect the glider to a hanging mass by a string the length of the air track passing over the bench pulley.
3. Set the data logging software to calculate acceleration.
4. Add adhesive substance 4 × 50 g masses onto the side of the glider.
5. Add 1 × 50 g slotted masses (0.49 N of force) to the end of the string.
6. Release the glider and record the acceleration.
7. Repeat this measurement two more times and average the accelerations measured.
8. Move one of the 50 g masses from the glider onto the hanger.
9. Repeat steps 6 to 8 until there are no more masses left on the glider.
10. At the end of the experiment, weigh the glider, masses, string and adhesive substance altogether.

### Results

It is important to record results in a suitable table, like the one below, which shows a set of example acceleration results in m/s2:

Force in NRun 1Run 2Run 3Mean
2.450.220.270.370.29
1.960.200.290.210.23
1.470.260.110.170.18
0.980.210.100.050.12
0.490.040.060.110.07

### Analysis

Plot a line graph with acceleration on the vertical axis and force on the horizontal axis. Draw a suitable line of best fit.

Describe what the results show about the effect of increasing the force on the acceleration of the object.

### Evaluation

Acceleration is directly proportional to the force exerted on the object. It is important to consider to what extent the results show this relationship. For example, do all the points lie on a straight line passing through the origin, or are there any ?

### Hazards and control measures

HazardConsequenceControl measures
Electrical applianceElectrical fault – fire/shockCheck mains cable and plug are not broken or wiring exposed before use
Masses and/or glider falling to floorObjects falling on feet – bruise/fractureUse relatively small masses and step back after releasing glider