Issac Newton said in his 2nd law : ‘The rate of change of momentum of a body is directly proportional to the external force acting on the body and takes place in the direction of the force.’
F rate of change of momentum
F change/time taken = (mv)/ t = m v/ t = ma
Diagram:
Equipment list:
- Light-gate
- String
- Masses
- 1kg trolley
- A ‘mask’
- Surface/slope
Method:
-Collect equipment
-Set up equipment (as shown on diagram)
-Attach the different masses on to the end of the string so it is running through the pulley.
-Release each weight making sure not to measure the acceleration once the weight hits the ground.
-For each weight measure the acceleration three times, this will enable you to take an average.
-Make sure the trolley is always starts in the same place. This will ensure that the test is fair , therefore giving the most accurate results possible.
In my experiment I have to use a ‘mask.’ This is a piece of card cut out especially so the light-gate can measure the acceleration of the trolley. The light-gate works on a set of timers that start and stop as it detects the card and the time when it doesn’t.
In my experiment I may come across the fact that friction may affect my results. I could compensate by adding small weights at the start so that the trolley moves at a constant speed or perhaps tilt the runway. In either case the acceleration should remain zero and therefore make no difference to my results.
Results table:
Analysis:
The straight line through my graph shows that acceleration is directly proportional to Force. This is in line with Newton’s 2nd law which I mentioned in my prediction. My graph shows me that my results were accurate as they agree with his law and prove that my prediction was right. Therefore the force is definitely proportional to the acceleration of the trolley. My results have a rogue result which I have highlighted in red.
Evaluation:
I think my results were fairly reliable all the repeats were consistent. There was one anomalous result, but that was expected. They were reasonably accurate with all values of acceleration to 1d.p or 2 s.f which was the same as the force. Each test was repeated three times and an average was taken, this improves the accuracy and makes my results far more reliable. I could further my experiment by a change in mass and repeat the experiment. I should get similar results, but the acceleration will always be less e.g
