When you don’t put oil on a surface, there will be a bigger grip if two surfaces slide against one another. This will result in more friction.
WIEGHT
MORE WIEGHT MORE GRIP MORE FRICTION
LESS WIEGHT LESS GRIP LESS FRICTION
Weight is due to the force of gravity on an object. On the earth the gravitational field strength is about 10N/kg… so every 1kg of matter experiences a downward force or has weight of 10N.
Weight is a force (gravitational pull) units: N (Newton)
Mass measures how much material, units: kg
The more the weight of an object, the more friction needed to move the object because when you put more weight it makes 2 surfaces grip together with more force.
The less the weight of an object, the less friction needed to move the object because when you put less weight it makes 2 surfaces grip together with less force.
SURFACE
ROUGH SURFACE BIGGER GRIP MORE FRICTION
SMOOTH SURFACE LESS GRIP LESS FRICTION
If the surface of car tyres is rough, there will be a bigger grip of the tyres and the road; therefore there will be more friction.
If the surface of car tyres has wearied away then there will be a smaller grip of the tyres and the road; therefore there will be less friction.
SURFACE AREA
BIGGER SURFACE AREA BIGGER GRIP BIGGER FRICTION
LESS SURFACE AREA LESS GRIP LESS FRICTION
The smaller the surface area, the less the contact with the other surface so there will be a lesser grip therefore this will result in less friction.
The bigger the surface area, the more the contact with the other surface so there will be a bigger grip therefore this will result in more friction, therefore more force will be required to move the oject.
CHOOSING A FACTOR TO INVESTIGATE
For this investigation I have been asked to choose a factor that affects friction and investigate it. Therefore I have chosen the factor – WEIGHT.
PREDICTION
My prediction for this investigation is that; the more the weight of the object, the more force will be needed to move the object because when you put more weight it makes 2 surfaces grip together with more force.
I predict that as the weight increase, the force will also increase. Therefore the weight should be directly proportional to the force. My graph should be similar to the one below. I also predict that if I double the weight the force should also double.
DOING THE INVESTIGATION
APPARATUS needed for this investigation.
- A block of wood (with a hook)
- Weights
- Newton measurer
- Weight measurer
- Flat surfaced wood -to do experiment on.
RISK ASSESSMENT
The safety precautions I need to take for this investigation are THAT I MUST MAKE SURE THAT I DON’T LET THE SPRING SNAP (NEWTON MEASURER).
Trial results
Before I did the actual experiment, I did trial results, which consisted of the first three set of weight to see if there is a pattern in my results.
From the trial results you can see that the first weight (N) that I started off with was 2.6N. This was the weight of the block of wood with the hook.
How I converted the weight into Newtons?
The weight of the wood was 260g, which is 0.26kg.
Weight (N)= mass (m) x gravitational field strength (g)
Weight (N)= mg
On Earth g = 9.8N/kg = 10N/kg
Weight (N)= m x 10
Mass of wood = 0.26kg
Weight (N)= 0.26kg x 10N
Weight = 2.6N
As you can see that I kept on adding 0.1kg (1N) each time onto the block of wood.
Form my trial results I know that as the weight increases, the force increases, so this means that I am ready to begin the experiment because the results I got from the trial experiment are efficient.
PLAN
For this investigation I will have to weigh the block of wood, to know what weight I will start to investigate from. I have done this in the trial results and I know that the block of wood that I will w using is 2.6N. to get efficient set of results I will measure how much force is needed to move the block three times. This way I can work out the average. I will then put a weight of 1N (0.1kg) on to the block, and drag it to se how much force is needed to move the block, which will have a total mass of 3.6 now. I will repeat this, so I have three results to work out the average. I will keep adding 1N and recording the results, I will keep doing this until I have measured the force needed to move the block with a total weight of 10N on top of it.
FAIR TEST
To make sure this is a fair test I will make sure I use the same surface to drag the block of wood across. I will also make sure that I use the same amount of force to drag the block, this force will be hard to keep the same but I will try my best to keep the same force when I pull the block. I will have to make sure I move the block at the same speed for all of the different weights.
I will now do the experiment, for the results table look on the next page.
RESULTS TABLE
Above are the results for the experiment that I did.
On the following page is the graph for the weight against the force.
ANALYSIS OF RESULTS
From my results I know that as the weight increased, the force needed to move the object increased. This means that the weight is directly proportional to the force. This means that my prediction was correct.
But by looking at the graph, I can see that I got a lot of anomalous results because only three of my averages met the best fit line and the rest are all above or below the line.
The reason why I had so many anomalous results was because it was not a fair test. The reason for this is that the force I used, to pull the block of wood was not the same force I used for pulling all the different weights. It was impossible for a human to use the same force when pulling an object because you cannot be exact. But if a robotic machine that is able to use the same amount of force to pull different weights had did this same experiment, then maybe I would have not had so many anomalous results.
But in my prediction I also said that if I double the weight the force should also double. I cannot say if it did by looking at my results table because if I double 2.6N I will get 5.2N. 5.2N is not a value that I investigated, so to prove this theory I will have to look at the graph to see if my theory is correct.
After looking at the graph I know that the force needed to pull:
2.6N is 0.85N
5.2N is 1.675N
so as you can see that roughly, as I doubled 2.6N, the force also doubled. But to make sure that this is not a coincidence, I will look at the graph and see if the force double as I doubled 4N.
The force needed to pull
4N is 1.3N
8N is 2.6N
This means that my theory is correct because as I doubled the weight of 4N, the force needed to move the weight also doubled.
Overall, my prediction was right because the weight is directly proportional to the force and also as the weight doubles, the force also doubled.
EVALUATION
From this experiment I can say that:
The more the weight, the more the friction therefore more force will be needed to move the object.
Name: Razwana Bi
Form: 11.4
Broadway School
Centre number: 20049
Candidate number: 0049
Plan and carry out an investigation to find out what factors affect friction.
