This is an example of a common experiment used to investigate friction and should help you understand how to work scientifically.
Aim of the experiment
To investigate the frictional forces on a mass being pulled down a slope of different gradients.
- 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.
- 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.
Care must be taken with masses.
|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|
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.
- 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.
- Your experiment is reproducible if others get precise measurements when they repeat it.