When the rider breaks the beam produced from Light gate 1, a recording is began by a computer linked up to both light gates. Once the rider cuts through the second light gate, then the timer on the computer steps automatically as the light gates can relay a signal to the computer.
A computer is used rather than the naked eye because the computer can be precise to 2 decimal places (d.p). Once the slide has passed through both light gates, it is moved around both light gates and the experiment is repeated. The variable for this investigation is force, that is controlled through the weights used n the pulley. The weights are changed at five separate times, at each time a different weight is used. My variables are as follows:
0.02 N , 0.03 N , 0.07 N , 0.08 N , 0.12 N ( N = Newtons)
The values I chose are all the smallest possible values that I am able to create.
In relation to safety, there are no specific safety issues that come to into play during this particular investigation, however behavior around the apparatus and the laboratory is always considered a safety issue.
The factors that are necessary to maintain as constants throughout the experiment in order to keep a high degree of accuracy are:
- Straight light gates (equidistant - 40cm apart)
- Same starting point of the rider ( 5cm before the initial light gate)
- Mass of the rider (0.400kg)
The light gates are required to be equidistant (40cm apart) and level in order to keep the test so accurate readings can be recorded.
The mass of the rider must also be mentained at exactly 0.400 kg because a slight chance in the weight will cause a change in the acceleration of the rider can result in widespread and inconsistent results.
It is also important to mention the starting point of the rider that must remain constant in order for the rider to pass through each light gate at the same speed during each repeat reading recorded.
In addition to these points of accuracy, there are others, which have sufficient relevance to the experiment.
The level at which the air track is must be kept horizontal so that the rider has neither too longer, or too shorter acceleration value that is recorded due to the slider being against or along the gradient of the air track. This can be simply modified by adjusting the track then leaving the rider without a weight and switch on the air track, if the rider remains stationary then the air track is horizontal.
The experiment will be measured on 3 occasions for each variable, these repeat readings will be averaged out into a single figure to gain an accurate set of results.
To prepare for the investigation, a preliminary test was carried out in order to discover which mass of the rider produced the most accurate results.
To do this, the lightest mass of the rider was used with the lightest and heaviest weights (0.020N - lightest) and (0.170N - heaviest).
The masses of the rider were the largest possible (0.400 kg) and the smallest possible ( 0.200kg).
The results showed me that the lighter the mass of the rider, the wider the range of results that I recorded. In contrast, the heavier the mass of the rider was, the more reliable my results were because they provided the smallest range. This meant that I chose the heaviest possible weight of the rider possible, which was 0.400kg.
Skill area O (Obtaining The Results):
Skill area E : Evaluation:
My results throughout my investigation, were very accurate. The spread of my repeat readings were very small, each reading for each strength of force were close together shown a high level of accuracy throughout the investigation. All my average points that I recorded are close to the best-fit line that I have drawn, which suggests that all my results have been accurately recorded and displayed in my analysis and obtaining evidence sections.
The procedures to which I applied my investigation were suitable because I was able to produce an accurate set of results with relative ease.
In my opinion, my evidence can support a sufficient conclusion that as that the force upon on object is directly proportional to its acceleration produced. My results were tested over a reasonable range and are considered accurate as they fit in with my initial theory and also they fit in with my initial predictions that I was able to produce.
I was able to produce these predictions by re-arranging Newton’s second law to show me what the acceleration of an object can b equal to in terms of its force and mass.
(Old equation)
Force = Mass x Acceleration
(N) (kg) m/s
(variable) (measurement)
(New, Re-arranged equation)
Acceleration = Force (mass / 0.400kg)
Mass
I have a range of values for my force, I inputted each one of these values to gain predicted results.
(When force = 0.02) : 0.02 = 0.05 (Actual average = 0.05)
0.400
(When force = 0.03) : 0.03 = 0.075 (Actual average = 0.07)
0.400
(When force = 0.07) : 0.07 = 0.175 (Actual average = 0.08)
0.400
(When force = 0.08) : 0.08 = 0.20 (Actual average = 0.20)
0.400
(When force = 0.12) : 0.12 = 0.30 (Actual average = 0.31)
0.400
As the above figures display clearly, my results are all highly accurate and sufficiently support my prediction and theory.
All that remains is to discuss how I can extend my investigation. The obvious point that springs to mind is to gather further results to obtain an exceptionally high level of accuracy. However, I can also look to change my variable from the force to the mass of the rider. I can do this by investigating the relationship between the mass and force on a rider to give me additional information.
I can carry out these tests in the same manner as I have discussed for this particular investigation, but changing the variables used. I will use a range of variables that will aid me complete my investigation reaching sufficient conclusions.
