The bigger the force on an object the greater the work done.
Energy
Elastic Potential Energy = stored in an elastic object when work is done on the object to change its shape.
Kinetic Energy = the energy an object has because of its movement. An object has more kinetic energy the greater its mass and speed.
Prediction
I predict that as the weight in the margarine tub is increased the distance it will travel is decreased. I think that the elastic potential energy will also decrease as the weight increases.
Diagram of apparatus
Method
- Set up the equipment as shown in the diagram on the floor.
- Mark with chalk where the legs of the stool are and the ruler.
- Using the Newton meter, pull back the elastic band with a force of 10N. Mark where the band stretches to with the chalk.
- Get the margarine tub without any weights in and pull it back to the chalk line using the elastic band. Measure how far it went using the metre rule. Record the distance in a table.
- Repeat another two times.
- Put two of the weights in the tub and do the same, recording the distance each time.
- Keep doing the experiment but increasing the weight by 20g each time. Do this until the tub weighs 100g.
- Find the average distance for each weight by adding up the three results and dividing it by three. Record the averages in the table.
Fair test
For this investigation to be valid and a success I will need to:
- Keep the stool, elastic band and ruler in the same place. I will check this before I do the experiment each time.
- Keep the same margarine tub as another one can make a difference.
- Use the same amount of pull on the elastic band, as more force shall make the tub go further.
- Increase the weight by 20g each time so the averages are fair.
- Do all the investigation in the same place because the floor is liable to be more or less slippy in other places.
Results
I am now going to work out the elastic potential energy in the elastic band so I can see if my prediction is correct. I shall do this by multiplying the force (10N) by the distance it travelled.
Conclusion
To be able to make a good analysis, I have drawn some graphs (see next 2 pages). From graphs one and two I say my prediction was correct, as the weight in the tub increased, the distance decreased. This happened in all three experiments and the average distance decreased too. From graphs three and four I can say that my prediction about the elastic potential energy was correct too, it decreased as the weight increased.
To make conclusions about the forces working on the tub I have drawn a diagram:
The thrust is provided by the energy from the elastic band, which makes the tub move forward. The drag is due to friction from the contact of the tub with the floor and air resistance.
This proves my prediction correct because all these forces were acting and this made the distance decrease as the weight increased.
The margarine tub gained more kinetic energy because its weight got bigger. The tub gained less elastic potential energy because the weight increased.
Evaluation
Overall I think my investigation was a success. I found the answer to the question “How does weight affect distance?” and I was able to draw conclusions from it. There were no anomalous results; on all graphs there are a smooth curve. This means that my prediction was correct and my results are pretty valid.
To improve the validity of my investigation I could use a larger range or take the averages of five results instead of three. I could also carry on making the tub heavier possibly to 200g or I could have bigger intervals like every 30g instead of 20g.
To continue my investigation I could find out what other factors affect distance e.g. force.
I carried out my investigation carefully, accurately and fairly so no errors occurred.
