Another effect, which may change the force needed, is Gravity. Everything on Earth has a mass and in result a downward force. Gravity acting upon the mass causes this downward force. It is this downward force (Gravity) that keeps us on the ground and the Earth orbiting the sun.
Predictions
I Predict that:
- The Greater the mass placed on top of the block, the greater the force will be required to pull it along the bench.
Diagram:
Apparatus List:
- Wooden Block
- Newton Meter
- 100g Weights x 20
- String
Method:
To find the effect of changing the mass of a block of wood has on the force needed to pull it along the desk, I will need to follow the method closely to ensure that the test is fair and achieves the correct results.
- Collect the required equipment.
- Set up the equipment as shown in the above diagram.
- Place 1 100g weight on the block and pull it along the bench with a Newton meter at a steady speed.
- Write down the force needed and the mass of the block.
- Add 100g onto the block.
- Repeat steps 1-4 adding on a 100g overtime you reach step 6.
Continue with this method until you have got results for a block of wood with 2000g (2kg). The experiment will need to be carried out more than once to enable me to produce a range of results, but also to obtain averages.
Fair Testing:
To ensure the test is as fair as possible I should do the following things:
- I must use the same block of wood and the same surface for my experiment. Changing surfaces or blocks of wood may lead to more friction present and therefore suddenly increase the force needed to pull the block.
- I must pull the block in the same direction at all times. Pulling the block across the grain in the wood will cause more friction and pulling the block in the same direction, as the grain will mean there is less resistance consequently meaning less friction and less force needed to pull the block.
Obtaining Evidence
Results:
The equipment was set up carefully and used safely throughout the experiment. The following results were produced during the experiment and no anomalies were present.
Analysing Evidence
1ST Test
2nd Test
Average:
Conclusion:
My hypothesis was correct. As I added more weight to the block, the more force it required to pull the block of wood along the surface.
This experiment proves that the amount of friction produced increases as more mass is added, which pulls the block closer to the surface making the collisions more severe and increasing the friction.
Evaluating
Evaluation:
The results in my experiment are accurate, but may differ from other people who carry out this investigation because there are several variables, which unless you used the same equipment will mean you get different results.
- Different surfaces/blocks of wood will have different surfaces. Some will be smoother than others. This would affect the results because the rougher the two surfaces moving across each other (in my case, the bench and the block of wood), the more friction that is caused. Therefore, rougher surfaces will require more force to pull them across the bench to counteract the extra friction. If the two surfaces were smoother, then less friction would be caused, so less force would be needed.
- The speed at which you pull the block of wood might also affect the force needed.
To extend and improve the experiment you could see how different surfaces, both on the desk and the block would affect the experiment. Also, you could adjust the speed at which the block was being pulled to see if this affects the force needed.
This in turn would provide me with a wider range of results.
