State your hypothesis – I predict that that as the mass of the pulley increases, the acceleration of the trolley will subsequently increase. However I believe that the acceleration can only increase to a certain extent hence eventually the acceleration will level off and remain the same.
What scientific knowledge has enabled you to make this hypothesis? The main theory that has enabled me to make this prediction is Newton’s Second Law of Motion. Newton stated that F=Ma; Force= Mass x Acceleration. This relationship can be turned into an equation by putting in a constant; F=constantxma. Force in physics, is defined as any action or influence that accelerates, or changes the velocity of a certain object. Force is a vector, which in other words means that it ha both direction and magnitude. The diagram below helps to explain the scientific theories. The trolley mass has been given the letter ‘M’ while the pulley mass has been called ‘m.’
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The gravitational potential energy is going to increase as the mass increases due to the fact that gravitational potential energy=mass x gravitational constant x height. If any of the numerous variables is varied however, the results could be totally different due to the energy either increasing or decreasing.
A theoretic formula that will aid me in this experiment is Mgsinx= (Mxm). This formula not only shows how crucial the variables are but also shows that the mass on the pulley has a direct effect on the acceleration of the trolley, this is a very important fact as I have chosen that the variable will be the mass on the pulley. Another formula that I am likely to use during this experiment is PE= mgh; where m= mass g= gravitational constant and h= height. Therefore altering the mass would directly affect the product and an increase in mass would result in a higher product. This is also the case the other way round. For example; if m=0.5kg; g=10N/Kg and h=0.2 then PE=1J
But if m= 0.8kg and the others remain constant then PE=1.6J
Kinetic energy is the same value as the gravitational potential energy as the pulley mass starts with no KE because it starts in a stationary position; 0J + 1.5J= 1.5J
Make a quantitative prediction of what you think will happen.
Justify your prediction using your scientific knowledge. The above graph is totally justified by the equation Mgsinx=(Mxm) In this case, ‘m’ refers to the mass on the end of the pulley, M to the mass of the trolley, g to is the gravitational constant and x to the angle of inclination of the ramp. I believe that the acceleration will cease to accelerate once a certain point is reached. This is the ‘tail’ on the graph. I believe this is going to happen due to air resistance and friction.
What factors might affect your investigation? (variables).
Mass on pulley- The mass on the pulley will affect the experiment as the more mass on the pulley will increase the acceleration of the trolley up the ramp.
Mass of the trolley- The less mass on the trolley, the faster the acceleration up the ramp.
Inclination of ramp- The inclination of the ramp is quite an important variable as a steep ramp will cause a slow acceleration and a shallow incline will have the opposite effect.
Ramp surface- Friction is also a key concern as the trolley will move faster over a smooth surface than over a rough surface.
Why do you think that these are important? I can only change one of these if the experiment is going to be a fair test. Any other changes, even a minute one will result with the reliability of the results being jeopardised.
How will you control the variables in order to make your investigation a fair test?
What are you going to measure and how? I am in effect going to be measuring the acceleration of a trolley of a set mass up a ramp. I will be using a ticker tape timer to measure the acceleration. This will be attached to the trolley using ‘blu tac’ and the trolley will have a mass of 500g in addition to it’s original mass. The trolley will be attached to a pulley which in turn will be attached to a mass that will be varied. Once the results have been taken, an average will be found after discarding any anomalous results.
Do you anticipate any difficulties? Hardly any difficulties will be encountered however; care must be taken when analysing the results to avoid recording incorrect results that will make the experiment unreliable.
How many results are you planning to take and over what range? I hope to take eight results though the absolute minimum is six. These results will be taken over a range from 0.3kg to 0.7kg. increasing the mass by 50 grams each time.
Say if you think you will need to repeat any results, and give reasons why. If possible I would like to repeat the results to provide a wider range and to counteract the anomalous results that are inevitable.
What apparatus will you require?
* Ticker tape and machine
* Clamp (to attach pulley to ramp)
* 1m Ruler
* Stand or Books ( to raise incline of ramp)
* 20 Mass ( 50g weights)
How will the equipment be set up and used?
* Use Books or stand to increase incline of ramp to 15ï¿½. Measure the incline using protractor.
* Attach pulley to edge of ramp, ensure that this end is placed off the edge of bench so that the mass has a decent distance to fall.
* Place ticker tape to lower end of ramp.
* Using the ruler, measure two metres for the trolley to travel.
* Attach string( 2m in length) to trolley, and to pulley.
* Place trolley at the base of the ramp and place 500g of weights on trolley.
* Attach ticker tape to trolley.
* Place weights on the string, that should be placed on the pulley. Begin with 0.3kg of mass.
* Turn on ticker tape machine and let the trolley go. NB. Do not push trolley, just let go of it.
* Record results, change the ticker tape and add another 50 grams to string, then repeat the 4 stages.
The diagram above shows how the apparatus should look once put in place.
What safety precautions will you take? This experiment is not dangerous hence no safety precautions need to be taken. However care must be taken while using the weights as the string could snap.
List the sources of information that you have used.
Complete Physics- Steven Pople
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GCSE PHYSICS COURSEWORK – RESULTS.
The results found are shown in the table below. These results have already been analysed and anomalous results have been ignored when finding the average.
When analysing the results I found that there were not too many anomalous results. However as expected there were some, these have been highlighted in blue. Most of the anomalous results occurred at the beginning of the experiment. This could have been due to human error which later did not occur as much because we had developed better ways of carrying out the experiment as the experiment progressed. Thankfully there were not too many anomalies and we had enough results to decide which results were anomalous and omit these and still have enough results to find an accurate, reliable average.
The average was then used to draw the graph shown below;
The graph shows that as the mass on the pulley was increased, the acceleration increased. To begin with this occurred quite quickly, however as more ad more weight mass added to the string, the acceleration was slower.
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GCSE PHYSICS COURSEWORK – CONCLUDING THE INVESTIGATION.
Both the graph and the results show that as the mass on the pulley increased so did the acceleration of the trolley. One might therefore think that my hypothesis has been proved but I believe that it has only been proved to a certain extent. To begin with the results were very similar to my prediction graph, however, the graph levels off far faster using the results from my experiment. This I believe could well be because the formula, although useful, did not include all of the variables, for example friction was not considered and friction is a key variable in this experiment. I believe that what could have happened is that the friction was far more than expected hence the trolley did not have a long enough ramp to overcome the friction and continue to accelerate. Another key point that has to be considered is energy. Obviously what was occurring in the experiment was as more and more mass was being added to the pulley, the gravitational potential energy increased. This in turn led to kinetic energy because the mass was falling, pulling with it the trolley. This therefore would obviously mean that the more mass that is added to the pulley, the more kinetic energy is being transferred to the trolley. My hypothesis has therefore to a certain extent because acceleration does increase as more mass is added and the results did tail off. Although the acceleration is clear, the levelling off is not as clear as I imagined would be present.
Overall this experiment I feel was very reliable. The experiment not only produced few anomalies but also produced reliable results which kept near to what I believed would be the case at the beginning of the experiment and there was a pattern present. Also, there were few areas where the experiment could go wrong, which always means less mistakes are likely to occur-hence making the results more reliable. There were a few things that could have jeopardised the reliability of the results such as the incline the ramp was at. The ramp could well have been jarred during the experiment, and the incline could have changed. Also, the method for measuring the incline had to be varied as the protractor could not be used due to the table being in the way. Instead of using the protractor, sine was used to find the angle by using the length of the hypotenuse and the length of the ‘opposite’ side by using the formula sine= opposite/hypotenuse.
This method was more accurate but did allow for another error to occur. (although I doubt it was the case) Also the ramp could have not been, flat, there was a possibility that it was on a slope which would have meant that the trolley would have been going across the ramp instead of straight up it. Although these problems could have occurred, I still believe that the results are reliable due to there not being too many anomalies.
The anomalies, although they did not effect my results too a great extent, are still an area of interest. These anomalous results, as pre-stated, were inevitable and even before the experiment began I knew that they would occur. In this experiment there a few possibilities of why the anomalies occurred. I’m relatively sure that the angle of the ramp remained the same so I don’t believe this could have caused the errors. What could have occurred is that the trolley was placed at different angles on the ramp each time which would mean that it would not be going straight up the ramp, but across it. Also, the trolley could have scraped against the edge of the ramp which would have slowed the ramp down. Also there is a chance of the ramp having different surfaces such as dust or dirt, this would have slowed the trolley down. All of these problems could have caused the trolley to change accelerations and cause these anomalies.
As in most experiments there are improvements that can be made. For example, as stated when discussing possibilities for the anomalies, the ramp could have had dirt or dust on it, could have been at an angle and there is a chance that the trolley didn’t travel straight up the ramp. All of these problems could have been avoided by using a little bit more care and ensuring that these things were not going to occur. Also, if possible I would have liked to have used a trolley with wheels that produced less friction. It was clear that the wheels created friction as all wheels do and although the friction did not change as the experiment progressed- hence not making the results unreliable, I still would have liked to have used a better trolley to ensure the results were reliable. Another area of possible improvement is to do with the releasing of the string.
An electromagnetic which would have eliminated any possible human interference while releasing the weights. The pulley also produced friction and a friction free (FF) pulley would have improved the experiment. Although air resistance is always present in everyday life hence is not expected to be stopped, a vacuum chamber could have been used to improve the experiment. This would have eliminated all air friction and improved the experiment. Also the ramp I found was too short and the distance of two metres did not give as much time to analyse the acceleration as needed in some cases, therefore a longer ramp should have been used
This experiment left great gaps that could have been investigated. I would have liked to have investigated other variables if it had been possible. Another possible experiment would have been to investigate different inclinations of the ramp. This was another variable which for obvious reasons was very important in my experiment. The ramp inclination could have been investigated by keeping the mass of the trolley and pulley remaining the same and only varying the angle of the slope changing. The best angles to use would be 0 degrees( in other words no slope) 10, 20 ,30 and 40 degrees. This would give a decent range.