I predict that as the weight on the block increases so therefore does the down force, increasing the amount of friction because it becomes more difficult for the ridges to pass over each and so a block with less/smoother ridges would find its passage a lot easier.
When the experiment was carried out, as I predicted, when the weight on the block increased so therefore did the Newton’s required to move it from a fixed position. The test was done with 2 Newton meters over 2 days. Using the same Newton meter was impossible as it broke. My results were as follows: Weight of block = 2.0N
In the first experiment weight was tested and a set of results produced. In this second experiment the surface area in contact with the desk will be tested.
To obtain my results I will use the following method, the block will be placed on two sheets of paper a measured distance apart with a Newton meter tied to it. The block will then be pulled and as it begins to move the amount of Newton’s required to cause this will be recorded. Each test will be done 5 times then averaged.
To make sure it is a fair test I will; as the same Newton meter ensuring non-introduction of new variables, use the same side of the block, use the same two pieces of paper and make sure the blocks movement is parallel to the supporting surface.
I predict that as the surface area of the block exposed to the desk increases so will the amount of Newton’s required to move it because there will be more sharper ridges to pass over therefore requiring more Newton’s. My results were as follows:
My prediction on 1 or 2 of the results was correct or partially correct but on the whole I fear my prediction was incorrect as it seems the surface area (exposed to the desk) does not greatly affect the amount of Newtons that is required to move it, any affect it does have is not continual and seemingly erratic.
The friction experiment has now been done with 2 variables: weight and surface area. I have now come to the third and final, surface texture.
To test the affect of surface texture on friction, I will, Place the block on the surface with a Newton meter tied to it, the meter will then be pulled and as soon as the block shows signs of movement I will record the amount of Newtons needed. Each test will be done 5 times then averaged.
To make sure it is a fair test I will: unless it breaks use the same Newton meter, I will use the same block and the same side of the block every time, I will use the same substance/type of substance for instance making sure the sandpaper comes from the same sheet. I will also keep the movement of the block parallel to the supporting surface.
Although smoothness is hard to measure I predict that the smoother a substance is to the touch, the less friction will be produced, because the smoother a substance is to the touch the less sharp or outstanding the ridges are, therefore the less resistance they cause.
Key
Substances:
Silicon based carbon paper: Si
Emery paper: Bs
Sand paper: S
Table top: TT
Plastic Bag: Pb
As I predicted the smoother a substance feels to be, the less it causes resistance, as shown in the results. I followed my method very strictly any variation caused by my hand is small to negligible, and would not greatly affect the results. I have come to the conclusion that for a substance to reach minimal resistance it can achieve this being light weight, smoothly textured and have minimal contacting surface area with the opposing surface. If a substance is required to have maximum resistance it would be the opposite.
I feel the experiment was performed rather well but there is room for improvement, to have maybe got fairer more accurate results I could have maybe repeated the experiment once or twice on all of them, then I would have more data to analyse giving me a better chance at accuracy. In all the three experiments instead of using the human hand to pull the Newton meter use a machine which would be less prone to inconsistency and use a table top free of blemishes. In the second experiment the block could have been placed on previously constructed platforms each measured to have 4 sides the same and those sides to be the measurements used meaning the non need of paper and a lot more accurate readings.
