Investigating friction
This is an example of a common experiment used to investigate friction.
Aim of the experiment
To investigate the frictional forces on a mass being pulled down a slope of different gradients.
Method
- Set up the apparatus as in the diagram.
- Pull the mass along the ramp using the force meter.
- Record the force needed to start the mass moving (this will be less than the force to pull it along once it is moving).
- Increase the height of the ramp to 10 cm to make the gradient steeper.
- Measure the force.
- Repeat by moving the ramp up in 10 cm intervals until 50 cm is reached.
An experiment to investigate frictional forces
Variables
- The independent variable is the height of the ramp (its gradient).
- The dependent variable is the force needed to pull the mass down the ramp.
- Controlled variables include using the same mass and ramp surface.
Risks
Care must be taken with masses, make sure that they cannot drop on to feet.
Expected results
| Height of ramp | Force needed |
| 10 cm | 21 N |
| 20 cm | 16 N |
| 30 cm | 10 N |
| 40 cm | 5 N |
| 50 cm | 2 N |
| Height of ramp | 10 cm |
|---|---|
| Force needed | 21 N |
| Height of ramp | 20 cm |
|---|---|
| Force needed | 16 N |
| Height of ramp | 30 cm |
|---|---|
| Force needed | 10 N |
| Height of ramp | 40 cm |
|---|---|
| Force needed | 5 N |
| Height of ramp | 50 cm |
|---|---|
| Force needed | 2 N |
What the results mean
The force needed to start the mass moving reduced as the ramp became steeper (the gradient increased). Fewer frictional forces exist when the ramp is steeper.
Evaluation
- Your measurements are accurate if they are close to their true value.
- Your measurements are precise if they are similar when completed again.
- Your experiment is repeatable if you get precise measurements when it is repeated.
