Prediction:
I think that when the the spring is compressed more, Will make the Trolley’s speed increase because the more I compress the sprint will mean the more potential energy it will have and when the springs released it will transfer this energy across to the trolley as Kinetic energy. I also think that there will be a pattern in the amount that the speed will increase for, I think that if you double the amount the spring is compressed it will double the speed. E.g. If the spring was compressed at 2cm and it might make the trolley travel at aprox 3m/s, then I doubled the amount the springs compressed by, so the springs compressed at 4cm, then the trolley should travel twice as fast at aprox 6m/s.
Also if I double the compression I’d double the amount of kinetic energy used. E.g. 1cm would be 10j, 2cm would be 20j, 3cm would be 40j and 4cm would be 80j etc
Method:
I did this experiment using a computer simulation but if I would of done this experiment to keep it a fair test I would of made sure that each time I did the test I’d only change in independent variables. I would of started by setting a spring loaded plunger behind a Trolley so I’ll be able to set the spring up compressed at different amounts, that when released will push the trolley, as the trolley is travelling I’ll read the amount of time that the trolley takes to pass a light gate and then from the amount of time it took to pass the light gate, I can work out how fast the trolley was travelling at.
Each time I’d do the experiment again I’d increase the amount that the spring is compressed, I would increased it by another Centimetre, by doing this I’d be able to see how much the speed of the trolley increases when I would raise the amount that the springs compressed. I’d do the experiment a total of 15 times, each time the spring will be one more centimetre compressed, so I’d have a reading of the time the trolley would take from 1cm up to 15cm.
When I release the spring It will push the trolley past the light gate, as the trolley passes the light gate, it will be measured on how long it takes for the trolley to pass, the light gate can then work out how long it took because it’s been programmed to know that the trolley was 10cm wide. Once I’ve got the speed that the trolley takes each time I can work out the sped of that by working out the formula:
Speed = Width of Trolley
Time
Equipment:
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Spring loaded Plunger - This is used to house the spring and compress it.
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Timer – This will be used to time how long the trolley takes to pass the Light Gate
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Light Gate – This sends out a beam of light and measures the length of time that the beam is broken when the trolley passes.
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Trolley – A small box on wheels which weights 1KG
Conclusion
From the results of the experiment it shows us that each time I increase the amount that the spring is compressed by another centimetre the speed that the trolley travels at increase on average by approximate another 4 m/s. Also from the results I can see that if we double the amount that the spring is compressed by centimetre the speed that the trolley travels at will also double, take for example when the spring was compressed at 2cm the trolley travelled at 7.646m/s and then when the spring was compressed by 4cm the trolley travelled at 15.220m/s. Whereas the kinetic of the energy follows a pattern of how much it increases because it doubles every time I increase the amount the spring is compressed by
The results I got from this experiment back up what I predicated because I said that I thought that the amount the spring is compressed by would increase the amount of kinetic energy transfer to the trolley and as the results show, every time the spring was compressed more the speed and amount of kinetic energy both increased. Also I predicted that I thought there would be some sort of pattern to the amount the trolley’s speed would increase by and as the results show there was a two main patterns in the results: Each result was on average 4m/s faster than the one before and also if you doubled the amount that the spring was compressed by the speed would also double.
Theory for prediction:
When the spring is compressed it will have potential energy which when released will transfer into mainly kinetic energy. If I follow ‘Hooke’s Law’ it will mean I’ll be able to figure out how much energy will be transferred from the spring to the trolley. So I know that as long as the spring isn’t over stretched or the spring isn’t too stiff that it will obey ‘Hooke’s Law’ which says that the extension, X of the spring is proportional to the force, F which produces the extension (F = KX). I’ll be able to find out the stiffness of the spring by the constant, K, which is called the Hooke’s Law Constant. The units K are either N/m or K/cm, for example: K will tell me how much the spring will compress or stretch for a given force. E.g. IF k = 20 N/cm, it will mean that a force of 20N will stretch or compress by 2 cm.
As well as working that out I can also work out how much energy is stored in the spring when it’s either stretched or compressed by taking a distance X. Then by working out the formula: Energy Stored = ½ K x X²
If there wasn’t any energy loss then all the energy in the spring (potential) would be converted into kinetic energy of the moving trolley. For example ½ mv½, where M is the trolley’s mass and V is its speed.
There is always some energy loss though, so there is never a 100% transfer of energy from one form to the other. This means that not all the spring's potential energy will be transfer into Kinetic energy.
Graph 1 – Speed of Trolley:
This graph shows that there was a steady increase and fairly even increase in the trolley’s speed ever time the amount the spring was compressed by was increased. The trend of this graph is of a positive increase (Linear).
Graph 2 – Kinetic energy of Trolley:
There is no pattern in the amount the graphic increases between each point, the only thing that the graph shows is that it follows a positive increase (non-linear)
Evaluation
Accuracy of results:
My results should be accurate because I used a computer simulation that should give me the correct results but the only way I could check this is if I set up the experiment and tested it all again rather than using the computer simulation.
Improvements:
If I wanted to improve this experiment more, I could try and change a few things which was done in the experiment or add on other variables and factors to the test.
I could try adding on another variable, this variable could be the distance that the trolley travels; this would help me see if the amount the spring was compressed by affects the distance that the trolley would travel or if it just changes the speed that the trolley travels at.
Another improvement I could make is by testing to see if when I double the amount spring is compressed by, always doubles the speed, e.g. would the speed of the trolley when the spring is compressed at ten centimetres be half the amount of when it’s compressed by 20cm.
Extending the experiment:
One extension to the experiment that I could do is by seeing if the weight oft eh trolley affects the speed it travels at. To do this I’d have to test the spring compressed at each amount at several times, each time adding a set amount of weight.
By doing this it could help me to find out two things. The first one being seeing if the speed is affected, if Trolley’s weight had changed the Trolleys speed The other one being to see if there is more of less kinetic energy in the trolley, if the speed is less there should be less kinetic energy.
