In this experiment, we are going to lift up a pen so that it has gravitational potential energy and let it roll down a ramp, gaining kinetic energy. When the pen rolls onto the carpet, the force of friction will do mechanical work on the pen and dissipate its kinetic energy. Mechanical work = force x distance moved. We will assume that the friction force is the same each time for the same pen on the same carpet, so if the pen rolls a longer distance, the pen must have had more kinetic energy to dissipate in the first place.
If we double the height of the ramp, the pen will start off with twice as much gravitational potential energy. My hypothesis is that it will therefore have twice as much kinetic energy at the bottom of the ramp and therefore roll twice as far.
So I'm prediciting: double the height of the ramp, double the distance the pen rolls on the carpet. This would mean a straight line through the origin graph - that pattern on a graph is called directly proportional.
1. Prop your science book or something similar up to the height given in the results table. We are going to be deliberately changing the height so that is the independent variable.
The independent variable is the one that you can write into the results table before you start. The independent variable is usually on the left hand side of the results table.
2. Hold a pen about 0.5 cm above the top of your book ramp and gently drop it onto the ramp.
3. It will roll down the ramp. Try to get it to roll straight. If it rolls off to one side, do it again.
4. Let it roll onto the floor - carpet is best. Measure how far it goes from the bottom of your book until it stops.
5. Repeat 3 times for each height of the ramp.
6. Calculate the mean by doing (1st go + 2nd go + 3rd go) = then divide 3 =
Always write the mean to the same number of decimal places as the readings.
7. You also need to be aware that the RANGE of the repeat readings for each height is (biggest repeat - smallest repeat)
and that there is a thing called the uncertainty = 1/2 x range of repeats
