P1: Motion down a ramp - CCEA

What are the variables involved in prescribed practical P1?

The main variables in a science experiment are the independent variable, the dependent variable and the control variables.

The independent variable is what we change or control in the experiment.

The dependent variable is what we are testing and will be measured in the experiment.

The control variables are what we keep the same during the experiment to make sure it’s a fair test.

In this experiment the:

• Independent variable is the height of the ramp.

• Dependent variable is the average speed of the marble. To calculate the average speed, we have to measure the time taken for the marble to travel a measured length of the ramp.

• Control variables are: the distance marble travels along the ramp, the mass of the marble, the type of marble used, the surface of the ramp, the initial speed of the marble.

Remember - these variables are controlled (or kept the same) because to make it a fair test, only one variable can be changed, which in this case is the vertical height of the ramp.

What equation is used to calculate average speed?

Average speed = \(\frac{distance~travelled}{time~taken}\)

What is the prediction?

As the height of the ramp increases, the average speed of the marble will also increase.

What is the justification for the prediction?

As the height of the ramp increases, the gravitational potential energy of the marble will also increase.

As the marble moves down the runway, its gravitational potential energy is converted to kinetic energy.

From the conservation of energy, the greater the amount of gravitational potential energy at the top, the greater the amount of kinetic energy at the bottom.

If the marble has a greater amount of kinetic energy at the bottom of the ramp, it will have greater speed.

This justifies the prediction that, average speed will increase as the vertical height of the ramp increases.

Large marble, adjustable support, ramp, marker pen, metre rule, 50 cm rule, stop clock, safety goggles.

Method

1. Set up the apparatus as shown in the diagram
2. With the marker pen mark a starting line, A, near the top of the ramp
3. Likewise, mark a finishing line, B, near the bottom of the ramp
4. Measure the distance between A and B with a meter rule. Record this distance in metres in a suitable table. This distance will remain unchanged throughout the experiment
5. Adjust the support so that the ramp has a vertical height at A of 5 cm. Measure the distance with a 50 cm rule and record in the table
6. Place the marble at A. Release from rest and simultaneously start the stop clock
7. Stop the stop clock when the marble reaches B. Record the time taken in seconds in the table
8. Repeat twice more and then calculate the average time. Record in the table
9. Calculate the average speed using the equation:
   average speed = \(\frac{distance~travelled}{average~time~taken}\)
10. Repeat the procedure for a total of 6 different vertical heights, increasing the height by 5 cm each time
11. Plot a graph of average speed in m/s on the y-axis against vertical height in m on the x-axis

Safety

• Secure the ramp with a G-clamp in the centre of the bench, so it doesn’t fall off on to someone’s foot.

• Make sure the marble doesn’t fall on to the floor and someone slips on it, a small carboard box could be placed at the end ofthe ramp to “catch” the marble.

• Wear safety goggles in case a marble hits someone in the eye.