Preliminary test
I have done a preliminary test at the height of 75cm to 55cm and a distance 122cm and the car mass is 123.7g.
Here are the results:
Length of the ramp: 1.22m
I find that it is too difficult the calculate the time taken, there is a lot of errors, so that I think I will do 3 times for each height and the average of each height to get a more accurate result.
Fair test
To have an accurate result, I have to make sure that my measurements are correct, the length of the ramp, the car mass, and the height of the ramp, every apparatus will also affect the results, so that it is very important to make sure those things are correct.
Method
Apparatus:
A ramp
A 1m ruler
A toy car
A stopwatch
First I need to measure the distance from the top of the ramp to the bottom to the ramp. I will measure the distance from the back of the wheel of the car and the mass of the car. I will set the height of the ramp to 50cm and decrease 5cm for each measurement; there will be total 10 readings. I will repeat each rolling experiment 3 times and find out the average time. The experiment will be like that:
Obtaining Evidence
Rolling distance= 1.22m
Car Mass= 123.7g
Gravity= 10m/s
Analysis
I have plotted a graph shows the height against the velocity, from the graph I can see that my prediction was right, the higher the ramp the faster it will go out the bottom of the ramp. Because the higher the ramp the more Gravitational Potential Energy(GPE), the more GPE the more kinetic energy converted and the car faster it will go. So that as the ramp increases, the velocity will also increase, when drag force equals to the downward force the car will reach the terminal velocity, so that the graph will be a curve, the car will not increase his speed as shown in the graph. There is a point is a bit out of the curve, perhaps this experiment cannot measure so accurate, the speed was to fast, so that errors will make very easily, but anyway it can still provide a graph as I predicted.
Evaluation
In this experiment, my method was not very good. When measuring the height of the ramp, it was not very accurate, this would affect the result. To prevent this I should mark the height on the stand, this would me more accurate. Also when measuring the time taken, you cannot measure it very accurately my eye, because it was too fast, we should use some electronic instruments to measure it or I practise more before I start the experiment, this will give a more accurate result. There was an anomalous result on the height 30cm, it is very difficult to avoid because it was too fast to measure the time taken. But at least I could plot a graph to show that my prediction was right.
I think I could start the height from the highest of the stand, then I could get more results and this can give me more evidence to support my prediction. And also I can try to use some electronic instrument to measure the time, this will make the measurement very accurate.
I think the results are not enough for each height, I think I should record more times for each height, and I think my the range is not too much, I think its better start from 1M than at 50cm, and decrease the height 5cm each time.
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The ramp was not enough, if I use a longer ramp, the timing will be more accurate.
From the graph, we can see that the curve was not curved enough; this is because there are not enough points for me, so my conclusion is not firm. As I said above, I should have a larger range result, then I can plot more points to let me able to draw a better graph.
