Prediction
I predict that the higher the ramp, the faster the toy car will go. I predict this because the higher the car is, the stronger the force of gravity on the car, and so the faster the car will go. The car will also gain speed (accelerate) as it goes down the ramp so it will start slower higher up but accelerate and finish at its maximum speed.
I also predict that the smoother the surface is, the faster the car will go and if the car is heavier, it will also go faster (mass won’t make a difference to the speed).
Equipment
- A toy car
- A ramp
- Books or a stool (to increase the height of the ramp)
- A stop watch
- A pen
- Exercise book (something to write on)
Safety
You may put a ‘wall’ at the end of the ramp to stop the car flying out and hitting anyone.
Method
- Get all the equipment and prepare it for it to be used
- Set the ramp and books (or stool) as shown in the picture in the next page.
- Pick up the toy car and place it at point ‘A’
- Make sure the person timing is aware and ready to time
- Let the toy car go (you can give it a slight push but make sure it is the same force each time)
- Say go or start when you are going to let it go so that your partner is aware of when the car will start coming down the ramp and knows when to press ‘start’
- When the car has reached the bottom (point ‘B’) of the ramp and your partner has stopped the stop watch, write down the time it took the toy car to come down the ramp. Also write the height and the distance of the ramp.
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Once you have written them all down work out the speed of each one ( S= D )
T
- Find out which one was quickest and check if your prediction was right!
- If your prediction WASN’T right try and work out why.
Preliminary Test’s results
From this preliminary test I found out that I should go from 5 to 70cm in height, because if it was higher it would be too hard to measure as it is too fast and it won’t be precise. If it was too low, the car might not start running and you might have to push it so it wouldn’t be a fair test.
Obtaining Evidence: Results
Anomalous results repeated
Analysing and considering Evidence
Graph 1
Graph 1 shows the first results recorded in the table of results above, as a line graph.
You can see that there are two anomalous results in this graph, which were then repeated and are shown in Graph 2.
In this graph you can see more or less what the relationship between the height of a ramp and the speed of a car is.
The higher the ramp = the faster the speed of the toy car
The graph shows two anomalies, but in graph two, these anomalies are then corrected by repeating the experiment. This shows that the anomalies aren’t part of what the results should show, but it was a problem of us doing the experiment. It could be that we measured the time wrong (either started or ended too early or too late) or that we pushed the car too hard and it started going faster and accelerated earlier.
Graph 2
Graph 2 is very similar to Graph 1 and shows the same pattern, but it is more precise as we repeated two points four times (anomalies) and so it looks as though it was a very accurate experiment and everything went right. From this, you can see that we should have repeated it more times, at least four, as the anomalies changed. Most of the points, except two, are the same as in Graph 1. All the points in this graph suit the line of best fit, while in Graph 1, two didn’t. They all fit into one relationship or pattern, with no anomalous results. Here, again, the pattern is:
The higher the ramp = the faster the speed of the toy car
Conclusion
My prediction was right and from the experiment I found out that the explaining of my prediction was also right, and so when the ramp is higher the speed will increase (the explanation to this is shown in my prediction). I also found out that there is no numerical relationship, the speed increases but not in a specified manner, it just increases, sometimes more that others.
I wanted to find out whether the difference in speed between lower heights (e.g. 5-10) was different to the difference in speed between higher heights (45-50).
I predicted that the difference would be higher at the start, when the heights are lower, that at the end when they are higher, because it is easier to measure, so it will be more accurate and at the end they all go quite quick so half a second will make a lot of difference, but stop watches aren’t reliable enough
So I looked at my results table (anomalous results repeated) and decided that the way to find out how much the speed increased from one to another, would be by subtracting the faster one from the slower one.
This is shown in the table below.
From this table I can see that at the start (5-10) it was the highest difference, but after that it varied. My prediction was partly right but mostly wrong. It might have been because there isn’t much difference in the heights so it would be much difference and not accurate, so this experiment isn’t really reliable.
Evaluation
Method
I think my method wasn’t bad and it is quite reliable, but not very accurate. This is probably because the stopwatch isn’t a reliable source for timing when it takes less than a second, because it can vary extremely. One tenth of a second can make a result anomalous, so you need some more accurate equipment if you want to make it precise, such as light gates
I also think that to make this experiment more accurate you could have a small wall at the end of the ramp (point ‘B’), that when the car reaches the bottom and hits the ‘wall’, the watch acts as an automatic stopwatch and stops at the same second the car touches it.
You could also have something at the top of the ramp (‘A’), like a clip, to hold the car and let go off the car automatically. It could be connected to the ‘wall’ at the bottom and also act as a stopwatch so the result would be much more accurate.
But even if you had very accurate equipment, you would still have anomalies because other things could go wrong, the environment could change the surface of the ramp or even weather conditions could make the car go faster or slower. That’s why you need to be very careful if you want to do an experiment on two or more different days.
I think we should have repeated the experiment more than twice, because as you can see in the graphs, only by repeating the anomalous results another two times, it made them fit into the relationship, when they didn’t before.
From this I think that it isn’t very reliable, as the anomalies changed very easily, the same way in which they could have changed to not fitting into a pattern again. But, the experiment is reliable enough to support the conclusion that the higher the height the faster the speed, because it worked like that most of the time. My conclusion is reliable enough to show to other people and trust it is right and that that is the way it will always work.
Further work that could be done to provide additional relevant evidence could be to do the same thing with a longer ramp and increase the height up to the point when the ramp was a straight line, so that would be the maximum speed. You could also change the surface of the ramp to see which surface made it go faster, or do it in different places, where it is windy, or sunny, or cold, hot the wind blowing east, west south or north. The (toy) car could have different weights and you could look at which one went faster, the heavier one or the lighter one.
By Maria Guisasola, 9.1.