When the gravitational potential energy is converted into kinetic (movement) energy as the car moves down the ramp, the friction between the wheels of the car and the surface of the ramp may use some of the energy; this can slow down the car, but only very slightly. The friction will not affect the results if there is the same amount of friction each time, to do this I will use the same car and ramp each time.
Prediction.
My prediction is that the larger the height is the faster the car will travel down the ramp because I know that the height affects the speed, this is because the higher the car is the more gravitational potential energy it will have and since the air resistance and friction will have no effect all the gravitational potential energy will be converted to kinetic energy, making the car travel faster.
In my experiment the variable will be the angle / height, I will keep everything else the same to ensure it is a fair test, I will use the same toy car each time and I will start the car at the same place to make sure each experiment is the same.
I have decided to use the angles 20,30,40,50,60,70 because this will give me a range of readings and I need at least 3 readings to plot a graph of results.
Apparatus – car, stopwatch, ramp, books, metre ruler, large protractor, box.
method:
- Collect your equipment and set up as shown in the diagram. Measure the angle and make sure it is 20°.
- Let go of the car and start the stopwatch. Time how long it takes for the car to hit the box at the bottom of the ramp. Record your results.
- Change the angle to 30° and repeat step 2.
- Repeat the experiment using angles 20, 30, 40, 50, 60, 70. Do each angle twice so that an average can be found.
Diagram.
Results.
Conclusion.
From my preliminary results I have found that the height of the ramp does affect the speed of the car – the higher the ramp is the faster the car will travel. This backs up my prediction, which I made earlier and I can relate my conclusion to my scientific knowledge because I already know that when the car is placed at the top of the ramp it has a certain amount of gravitational potential energy, which is converted into kinetic energy when the car travels down the ramp. So the higher the ramp is, the more gravitational potential energy there will be to be converted into kinetic energy, resulting in more kinetic energy making the car travel at a faster speed.
From the line of best fit on my graph I can see that there must be a pattern because there is strong positive correlation between the points and there is a straight line, which shows that the height and the speed are in proportion to each other.
On my graph I have drawn dotted lines up to the curved line to find the results I should have according to the line of best fit. These are shown in a table and allow me to see where I have any errors in my experiment.
Evaluation.
I think my experiment was quite a good one because my method was clear and easy to follow and my results were mostly accurate. There are 2 points on my graph which do not fit the line of best fit, there are many possible reasons for this as I found many problems in my experiment – I planned to use the angles 20,30,40,50,60,70 ° but I found that it took a lot of books to gain the correct height for the angle to be 20 °, if I had gone any further than 20 ° it would have took up too many books and would have been dangerous for the ramp to be so high in case it fell on someone. I will overcome this by measuring the height on my actual experiment instead of the angle. We began by using different people to time the experiment but I think it would make the investigation fairer if one person timed it. There is also error in stopping and starting the stopwatch because reaction time may be delayed. In the actual experiment I will overcome this by using light gates, I cannot use the large ramp and toy car because the light gates are only 7.5 cm wide so I will use a narrow ramp and a marble or ball bearing. I found it difficult to get the exact angle using the protractor so I am going to measure the height next time and I will calculate the angle using trigonometry. These problems could all cause my results to be out and I don’t think this experiment was really precise enough to support my conclusion that the height affects the speed of a toy car.
From my preliminary work I have decided upon an experiment, which will give me accurate results enabling me to come up with a precise conclusion. I will take 5 readings to ensure I get accurate results and so that I can plot a graph. The variable will be the height the car travels from and the things I will keep constant are the same ball bearing each time and the same light gates, laptop and track to ensure it is a fair test.
Prediction.
I can make a prediction that the higher the ramp is the faster the ball will travel. I can relate this to my scientific knowledge from the beginning; that the higher the object is the more gravitational potential energy it will have and there will be little air resistance and friction so all the gravitational potential energy will be converted to kinetic energy, making the ball travel faster. I can also relate my prediction to my preliminary work in which the higher the ramp was the faster the car travelled.
Apparatus:
ramp, ball bearing, light gates, laptop, weights.
Method:
- Collect your equipment and set up.
- Place 2 weights under the track and measure the height.
- Place the ball on the ramp and allow it to roll down the track. Record the result (shown on the laptop).
- Repeat the experiment, recording the height and time each time.
- When the experiment has been completed once, repeat it so that you get 2 sets of results.
Diagram.
Results:
* The distance was always 0.5 metres.
Conclusion.
From my results I can see that the higher the ramp was the faster the speed of the ball bearing, as I predicted in the beginning, this is because the higher the object is the more gravitational potential energy it will have and there will be little air resistance and friction so all the gravitational potential energy will be converted to kinetic energy, making the ball travel faster.
In my results I can see that there is a pattern, the points are mainly on the straight line, which shows that the height and speed are connected, they are proportional to one another. I can see this because as the height increases the speed increases showing that the height is a factor, which affects the movement of an object.
On my graph I have drawn dotted lines up to the line of best fit which will allow me to see what results I should have got for the 3 results which are out. These are shown in a table on my graph.
In this experiment I decided not to measure the angles as I did in the preliminary one, I used the height instead but I can calculate them using trigonometry to compare them with the preliminary experiment:
The formula for gravitational potential energy is:
Eg = mass x gravity x height.
As the mass in each experiment was 0.05 kg and the gravity was 10 I can use the formula to calculate how much gravitational potential energy the ball had and therefore how much kinetic energy it had:
From my results I can use the nth term to try to find the relationships between the speed, I can then work out a formula:
height 1.7 3.5 5 6.8 8.5
speed 0.30 0.47 0.61 0.70 0.80
1st difference 0.17 0.14 0.09 0.10 2nd difference
0.03 0.05 0.01
I looked for the 1st difference and then the 2nd difference however I could not find any patterns so I cannot form a mathematical term for the results.
Evaluation.
I think my experiment was quite a good one because my method was clear and easy to follow and my results were quite accurate. I was able to use information, which I had found out in the preliminary experiment in order to carry this one out successfully by using a precise method, which was accurate.
There were 3 results which were slightly off the line of best fit on my graph this could be because the light gates were not working correctly or the laptop didn’t record the correct results. I could improve the method by doing the experiment more to ensure accuracy although I used precise equipment so the results should already be quite accurate. Although there are still some slight errors in the experiment I think that the evidence is good enough to support my conclusion and prediction, which is the higher the ramp is the faster the object will travel. To improve my investigation and extend it I could use a digital meter to make the results more accurate, if the experiment was to be extended we could use other vehicles to roll down the ramp, using different size, weight and type of wheels to see if this has any effect on the speed.
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