After that we attach a length of string to the trolley and tie it to the mass hanger. The length of the thread must be long enough for the mass hanger to hit the ground before the trolley reaches the end of the runway. Secondly we measure the height the mass will fall to be able to then calculate the GPE and if we had to check later on or repeat the experiment we would have to use the same height in order to keep it a fair test. Later we attach a length of ticker tape to the trolley and pass the other end through the ticker-timer.
Starting Up The Process: We release the trolley so that the falling mass accelerates it until the mass hits the ground. After this, the trolley will move with constant velocity. We can check this using the ticker tape; the dots will be at an equal distance once the falling mass has hit the ground. The longest distance is measured and divided by 0.02. These steps are then repeated but with an additional mass, all experiments with the same falling mass MUST be repeated at least 3 times taking 5 measurements and controlling all dependant variables to make sure that the results are fair and that we have a wide range of the results making sure that we don’t depend our conclusions on a faulty result.
Safety:
The person measuring the height of the falling mas must keep a certain distance from the weights as they fall.
The runway must be securely positioned to prevent it falling on anyone, they are also very heavy and require two people to carry it.
Rulers can be used to make sure the trolleys don’t change direction and hurt somebody.
Conclusion:
We chose to plot this graph velocity against falling mass because they were independent variables and the rest stayed the same:
MGH=1/2MxV stayed the same
According to the table, the experiment didn’t actually prove the law of conservation of energy, the initial GPE and final KE would have had to be the same because we compensated friction that means no energy was to be wasted as heat or sound. But the results stated that we got more KE than GPE, which goes against the Law because energy can’t be created or destroyed. This could be due to experimental error, may be we didn’t compensate for friction enough causing it to slow down, the graph also implies experimental error, or inaccuracy because it presents results that are very scattered.
On the other hand my prediction was right, when the falling mass increased, the velocity did too this also means that as the falling mass increased kinetic energy did too. This proves the law of conservation of energy, because the GPE (mass of the falling object) is transferred into KE so the velocity increases, the more initial GPE (mass) the more KE (velocity). The line of best fit proves this, which is straight, and means that velocity and the falling mass are directly proportional if our results would have been more accurate then this statement would have been more obvious.
Evaluation:
The method didn’t work exactly as planned, I don’t think we made any experimental error as we controlled each variable well but I suppose that the increase of KE can be due to the fact that we might have elevated the ramp fat too much causing it to accelerate and increase KE.
Yet the experiment isn’t very reliable. It is impossible to show the law of conservation of energy with this experiment because energy will always be wasted in the form of thermal or sound energy due to friction. The practical could have been made more reliable if we tried compensating for friction more or carried it out more slowly then the results would have been much closer.
We didn’t have any anomalous results but to reduce experimental error and get our results more accurate, other pieces of equipment could be used to measure the velocity e.g.: light gates that are circuits that have an opening between them and if it is interrupted a signal is sent to a computer or even data loggers could be used. Also compensating for friction is one of the main drawbacks in this experiment and should be kept a closer eye on or previously checking if the trolley travels at a constant velocity. The height must me measured well, because if the experiment is again repeated and the height isn’t right it would give the falling mass a greater GPE so the results wouldn’t be reliable. Validity is another very important aspect, the more readings the better because it is less likely to get unreliable results, rulers may be used to create a sort of railway for the trolley not to change direction so the distance travelled is always the same.
For more experiments in this field, varying the height s in which the falling masses drop can prove that GPE depends on the height of an object. This also can demonstrate that with more GPE input more KE output, as while varying the heights the higher the object the more initial GPE so the more final KE.