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Note: The string needs to be long enough to allow the vehicle to start at one end of the ramp and the mass to be held over the edge
of a bench/air track via the pulley. The Voyager can be used with a clamp stand or simply placed on text books. If using clamp
stands, do not clamp Voyager too tightly. Ensure that the light source shines into the SmartEye as this change in contrast between
the light source and black card will allow Voyager to ‘see’ the card passing. The mass used depends on the vehicle being tested. Our
experiment was performed using up to 25 grams in 5 gram intervals on an air track so you may require more mass. (The air track car
had a mass of 330 grams.)
Method:
1. Starting with 5 grams, release the mass and record the acceleration of the vehicle passing the Voyager.
2. Repeat, using the same starting point each time, to obtain at least fi ve readings and obtain the average acceleration.
2. Place another 5 g mass onto the holder and put the vehicle at the same start point.
3. Release this new mass and record the new acceleration repeating fi ve times.
4. Repeat this for each available mass.
5. When fi nished the results can be printed, saved or transferred to a spreadsheet for more analysis.
Note: If you obtain some strange results, this can usually be attributed to a false trigger of the light ‘gate’. This can happen if a hand
or other object inadvertently passes through the gate. You can also get false triggers if the ambient light changes suddenly, for
example bright sunlight falling on the sensor part way through an experiment. On the air track shown it is diffi cult to lift the car over
the SmartEye sensor so the return acceleration (usually negative) was ignored.
Results:
For each result, convert the mass attached to the vehicle into Force by converting to kilograms and multiplying by acceleration due to
gravity. Some pupils may prefer to take ‘g’ as 10 ms
-2
rather than 9.81 ms
-2
eg. for 10 grams => 0.01 kg x 10 ms-2 = 0.1 Newton
force applied.
Plot a graph of Force on the ‘y’ axis against Acceleration on the ‘x’ axis.
This should give a straight line graph as shown.
Discuss what the gradient should be.
Ask the pupils to determine why the line might not pass through the origin.
The gradient should give the mass of the car being used since F=Ma and y=mx+c
for a straight line graph.
Going further:
Using this setup, could you investigate the Force and Speed relationship?
How could you minimise the problem of friction in this experiment? If using an air
track, what about air resistance as the car moves?
Physics
