We went up to 65cm because it’s the highest the clamp stand will go and we started at 15cm because below that the trolley will hardly move.
We have chosen to use a light gate as we found it a much more accurate method of measuring as it can measure to the nearest 100th of a second. Rather than measuring the run off distance with a ruler which measures to the nearest mm, and timing it with a stopwatch using the your finger to stop it which can only measure on average to the nearest second.
We have chosen the light gate to be placed 75cm down the ramp because it would give the trolley sufficient time to build up enough momentum.
We have chosen a 1kg trolley, as it is an easy number to work with; it’s a unit load therefore there would be no decimals involved, if we had to use a 1.678kg trolley it would be easy to make mistakes in our calculations. Also it will give enough mass for it to keep in the same direction.
Method:
The first thing we will do is set up the equipment as in the diagram, and set up the laptop that the light gate will connect up to. Then we will turn on the laptop and go on the program ‘Timing’ via Start, Programs, Science and then down to timing. We will then make sure that the measurements or units are correct on the program. Also we will check that the light gate is 75cm down the ramp. Once we have checked that everything is correct we will click Start on the Timing Program (screen). Then we will get a 1kg trolley and put it at the start of the ramp lining up with the light gate and then let the trolley go gently without aiding it with a push. When the trolley goes through the light gate it breaks a beam within the light gate, this breaking of a beam tells the timing program to record the result. If the attempt was successful we will record the result on our results table. We will do this 3 times to gain an average to make the experiment more accurate, or maybe 3+ times if the trolley did not complete a successful run down the ramp. But we will only take 3 of the closes results together for the average. We will then repeat the whole process for heights 20cm-60cm going up in fives.
Fair Test:
To make my experiment a fair test I will keep these things the same:
- The Ramp
- The light gate measurement (75cm form the top of the ramp)
- Trolley
- Clamp Stands
We will keep the ramp the same because it will have a different amount of friction to another one. Also there may be dints and marks in others that would produce more friction therefore there will be less PE changing into KE, as there will be less velocity.
We will keep the light gate measurement at 75cm because if we changed it there will be either more or less PE being transferred into KE consequently you would be getting inaccurate results.
We will be keeping the trolley the same because some trolleys have they wheels worn down more than others do. So there will be a change in friction resulting in more or less waste energy being transferred and more or less PE being transferred into KE.
We are going to keep the clamp stands the same because some of the clamp stands have different grips, so some might slack and loose it s height position a bit. Again this might result in inaccurate results.
Results:
The 1.5 is a anomaly, because compared to the other results for this height its too big.
Conclusion:
I found out that the higher the ramp the higher the speed of the trolley. This agreed with my prediction that was based on the theory:
Potential energy lost = Kinetic Energy gained
When an object rolls down an incline; the object is becoming lower to the ground, therefore the potential energy decreases and transfers into kinetic energy, until it gets to the ground where a complete energy transfer has taken place into kinetic energy. In other words the lower it gets the faster it goes.
This diagram above shows a trolley going down ramps with two different heights. There is an energy transfer happening. At the top of the ramp in both diagrams the transference of potential energy into kinetic energy has not taken place. However when the trolley starts to roll down the incline the transference begins, when it is half way down the ramp the energy is shared equally. From then on the kinetic energy is gaining more and more over the potential therefore becoming faster and faster, and then the trolley reaches the end of the incline, now a complete energy transference has taken place.
As you can see the higher the ramp the more potential energy there is consequently there is more kinetic energy being transferred making the trolley go faster.
Rearranging the formulas to get velocity on its own means I can support my conclusion just by putting in different heights from the result table.
Potential Energy Lost = Kinetic Energy Gained
PE = KE This just means, when something falls its potential energy is converted into kinetic energy, hence the further it falls the faster it goes.
PE = KE
mgh = ½ MV2
V2 = mgh
½ x m
V2 = mgh
½ x m
V2 = gh
½
V = √(2 x gh)
V = √(2gh)
1.
h = 20.0cm
g = 10 m/s2
V = √(2gh)
V = √(2x10x0.2)
V = 2.0 m/s
2.
h = 40.0cm
g = 10 m/s2
V = √(2gh)
V = √(2x10x0.4)
V = 2.83 m/s
As you can see the theory is right. The velocity has increases when the heights are increased.
Here is some results from my results table this is to help justify my conclusion further.
As you can see there is a profound difference in the speeds reached between the two heights. Again this shows the higher the ramp the faster the trolley will go.
This is a height from the graph to prove the theory further. I have chose 40cm as you can see it has been proved.
Look On Graph
40cm = 2.26 m/s
Here is the calculation for 40cm
h = 40.0cm
g = 10 m/s2
V = √(2gh)
V = √(2x10x0.4)
V = 2.83 m/s
As you can see 40cm gives you 2.83 m/s, however on the graph the answer was 2.26. The difference in the two answers is due to wasted energy like friction, which is built up on the ramp. This building up of friction would of made the trolley move slower therefore would not of reached its full potential which is around 2.83 m/s.
The results differ to the actual experiment because the calculator does not account for the wasted energy e.g. friction on the ramp.
Evaluation:
The experiment was quite reliable it was very accurate therefore it gave a good conclusion. The graph did not produce any anomalies and produced a strong correlation, making the experiment more reliable.
The accuracy of the equipment was pretty good. The light gate measured to the nearest 100th of a second so there was nothing to really improve on that. The clamp stands had a limitation of the height it was able to reach it could only get to 65cm also the clamp stands tended to slip a bit so we could not get a completely accurate result.
To improve the clamp stands you could make a bugger one to get a larger set or results, as the ramp would able to become higher. Also they could have the same grip as a pair of pliers instead of a screw. Pliers are meant to hold on to things therefore they would work well on a clamp stand; here is a diagram to help explain.
The trolleys were all right at accuracy but they had a couple of downfalls. The wheels on them were not perfectly smooth this produced friction, also the case of the trolley sometimes dragged along the floor causing more friction. To improve this you could smoothen the wheels with glass paper and you could cur off the bit of the case that was scraping along. The ramps were not very accurate as used a wooden one with dints and cracks in it, this was causing friction for the trolley and sometimes putting the trolley off track if the light gate. To improve this problem you could sand the ramp down producing a much smoother surface or you could use a metal ramp this would not be as prone to dints as wood as its a lot stronger.
The experiment is reproducible, you can see it is by looking at these results for 60cm and 35cm.
Also we got a good set of results which gave a good conclusion. Using a height and calculating the result and comparing it to the same height on my graph can prove this:
Calculation for 15cm
h = 15.0cm
g = 10 m/s2
V = √(2gh)
V = √(2x10x0.15)
V = 1.73 m/s
Reading from graph for 15cm:
1.26 m/s
As you can see the readings are not exact but they are similar, the reason why they are not the sane is because the calculator does not account for friction or other wasted energy.