Moment= 4N x 3cm= 12cm
Moment= 4N x 4cm= 16cm
Moment= 4N x 5cm= 20cm
As I predicted before the moment would be bigger at 5cm from the pivot.
Link Statement:
The methods to both coursework are very similar and they use the same equipment. As well the coursework are similar as they both depend such as distance from the pivot or the weight of the load hung. In both course works the dependent variable is the amount of deflection. As well the methods to both of the coursework are very similar as they are set up in the same way but the independent variables are different. In my preliminary course work the independent variable was the distance the weight of a load was hung and the control was the weight of the load. However in this second coursework the independent variable is the weight of the load and the control is the distance the weight of a load is hung.
Diagram:
Equipment:
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1 wooden metre ruler- I will use a ruler with millimetre and centimetre markings so that the length of the cantilever can be measured to the nearest millimetre; this should provide an appropriate level of accuracy to prove that the deflection is proportional to the mass applied
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1 wooden 50cm ruler -I will use a ruler with millimetre and centimetre markings so that the deflection can be measured to the nearest millimetre; this should provide an appropriate level of accuracy to prove that the deflection is proportional to the mass applied
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G- clamp – to hold the wooden metre ruler
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Load- 1N, 2N, 3N, 4N, 5N, 6N, 7N, 8N- this will give me a wide range of results.
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Retort stand, boss, clamp- it will keep the 50cm ruler straight at a constant level
Method:
- I will set up the apparatus as shown in the diagram above with the length at 70cm.
- I will then measure how far the horizontal ruler is from the floor against the vertical metre ruler.
- Next I will put a load of 1N at 50cm from the pivot and measure how far the horizontal ruler is from the floor against the vertical 50cm ruler in millimetres- I will measure above the ruler rather than below it.
- I will then repeat step 3 but with 2N, 3N, 4N, 5N, 6N, 7N, 8N loads at 50cm from the pivot.
- I will then have repeat steps 2-4 a further two times to ensure that there are no anomalous results and so an average can be calculated.
Variable Table:
Fair Test:
I must keep the distance from the pivot the same because both the distance and weight affect the amount of deflection. Deflection happens as moments bends the ruler not just the distance from the pivot or the weight o the load. The formula for moment is Moment= Force x Perpendicular distance from the pivot. So if I change both factors the test will not be fair.
I must keep the material of the ruler the same because different materials have different amounts of particles. A metal rule has more particles than a plastic ruler. Also a metal ruler will not bend as well as a plastic ruler, which could snap. I will do this by only using a wooden ruler as the cantilever.
I must keep the length of the ruler the same because different lengths of ruler have a different amount of particles. I will do this by using the same length ruler which is 1 metre.
I must keep the thickness of the ruler the same because the thicker the ruler the less it bends. The thinner the ruler the more it bends and it will snap easier. I will keep the thickness the same by using the same rulers.
Safety:
To ensure that there is the optimum level of safety for myself and others I must: Be careful when I am handling the weights as they can drop on my feet.
Be careful with the ruler as it returns to its normal position.
Make sure there is know in the ruler as it could break and cause splinters.
Obey the safety rules already emplaced in the laboratory.
Prediction:
I predict that as the weight of the load increases so does the amount of deflection. So if the weight of the load decreases so does the amount of deflection. This is because the deflection is affected by both the distance from the pivot and the weight of the load. This can be defined by moments which are the rotation caused by a force acting at a distance from the pivot. A moment is classified by the following equation:
Moment= Force (N) x Distance (cm) from pivot
The force in this investigation is weight (N). So if I changed the weight of the load but kept the distance from the pivot the same- The moment would get bigger as the weight increases.
I also predict if you double the weight of the load so the amount of deflection also doubles. So if the weight is 1N and the deflection is 10mm. the deflection should be 20mm if the weight is 2N. This can also be said for Hooke’s Law which us the extension is directly proportional to the stretching force. So if you double the load, the extension will also double and if you triple the load, the extension will also triple. This will happen until the spring reaches its limit of proportionality, in which the spring will become deformed permanently and can never return to its normal shape.
Results Table:
Test 1
Test 2
Average of Both Tests
Graph: Attached
Analysis:
My prediction was right because my graph shows as the weight increases, so does the deflection. It also shows the weight decreases, so does the deflection. This means as the force gets bigger so does the moment and as the force decreases so does the moment. Moments cause the deflection to happen not just the weight of the load as said in Hooke’s Law (the extension is directly proportional to the stretching force. So if you double the load, the extension will also double and if you triple the load, the extension will also triple).
I can prove this because in my preliminary coursework the independent variable was the distance from the pivot and the control was the weight of the load and yet the still deflection occurred. The amount of deflection increased as the distance from the pivot increased. This shows that moment bends the ruler.
This is the formula for moments:
Moment= Force (N) x Distance from the pivot (cm)
As well the deflection is was not directly proportional to the weight of the load. This means that my second prediction did not come true which was (if you double the weight of the load so the amount of deflection also doubles). I can prove that this is did not come true. It is shown on my graph and the table below.
Only one result approximately doubled the average of deflection when the weight of the load doubled that was 6N.
Evaluation:
My method was safe, clear and fair as the experiment was carried out fairly accurately. However I did receive one anomalous result which was when the weight of the load was 2N.
2N was an anomalous result as it should have been approximately between 16mm and 18mm. This could have occurred because.As the ruler was clamped on one end and on the other end the weights were hung there was a ruler that was clamped along with this ruler so that the deflection could be measured but both of these rulers had a bent initially because of its own weight but these deflections were different hence this slightly affected my accuracy of my final result. Also I could have measured below the ruler rather than above the ruler as said in my method. The reason for doing my preliminary results was to get an indication of the patterns that would occur in the results. Also, it was a practice so if I made any mistakes then, they could be fixed so that for the real experiment, minimal mistakes would be made. When I look at my preliminary work, I can see that the diagrams are exactly the same. From this I can see that the method is nearly the same except in this investigation the independent variable is the length of wire whereas in my preliminary investigation the independent variable was the cross- sectional area of the wire.
To ensure that no anomalous results take place again I will always measure above the ruler
My results were reliable but to make them more reliable I should have repeated the experiment 3 or 4 times to achieve better reliability. But there was not enough time permitted to this repeat the experiment 3 times.
To further my investigation I could change the independent variable to the material of the ruler. The dependent variable would be the deflection. The controls will be the distance from the pivot, weight of the load, length of the ruler, thickness of ruler.
