The 1st stage of my preliminary work was to find a suitable type of elastic band to use within the experiment. Ideally we needed a band that would be able to be extended easily, and that could travel at such a speed, so that a reading can be obtained easily and to the best accuracy. I collected a number of different sizes and width elastic bands and catapulted them of the end of a meter rule against a wall. I chose from a choice of a

- Short, thin elastic band
- A short thick, elastic band
- A long thin elastic band
- Along thick elastic band.

We immediately ruled out using the short thin elastic band as it was (1) hard to extent, which would mean it would be hard to extent to various length, so I wouldn’t be able to get a varied range of readings, and (2) because when the elastic band was released of the end of ammeter rule, it travelled much too quick and high, in that I couldn’t determine an accurate reading. The elastic contained too much tension within it while it’s being extended.

We had slightly the same problem with the short thick elastic band, except it moved at a slower rate, so it was easier to determine a reading. However we found that the best elastic band was the long, thick elastic band, because it’s heavier therefore it’s going to move through the air at a slower speed against the resistance, and will reach a height to which I could obtain a suitable reading. It’s also easier to extend to the length required. So I believe that this band will provide us with the most accurate, varied range of results.

The next stage is to identify the range of units to which the band will be extended to. I worked from the length of the elastic band which is 0.18m and each time extended it by 0.02m each time till extension of 0.08m, where the height will be the maximum to which we can determine a reading accurately.

I decided to repeat my experiment 4 times over in order to establish a reasonable average result for each unit the band is extended, and to produce a good plotting point for each result on my graph, in order for myself to be able to distinguish a pattern within my readings.

Prediction

To predict what could possibly be the outcome of the final experiment, I carried out another pre-experiment. In which I attached an elastic band (the same one that is to be used in the final experiment) to the end of an Newton meter, I pulled the band and extended it to the same distances as we are going to use in the final experiment, and measured the force of the extension. We measured the extensions using a meter rule. We were left with a group of results like so:

Length of First result Second Average

Extension (m) (N) Result (N) Result.

0.02 0.9 1.1 1N

0.03 1.4 1.6 1.5N

0.04 1.4 1.6 1.5N

0.05 2.1 2.3 2.2N

0.06 2.7 2.1 2.4N

0.07 2.5 2.9 2.7N

0.08 3 2.6 2.8N

This tells us that as the length of the extension increases, so does the force of the extension. So if more force is applied while the band is being extended, as the band is catapulted it will achieve a higher height, because there is a grater force that is within the band that is able to push against the resistance of the air easily.

It also tells us something about the conservation of energy. While the band is being extended, it holds a lot of stored energy within it, otherwise known as potential energy. As the band is released this potential energy is transferred into motion energy, known as kinetic energy, which is the transferred gravitation potential energy, while the band is moving through the air and against the gravitation forces acting upon it.

So therefore all kinetic energy produced will convert in to gravitational potential energy as the band is released. Also as the graph states the bigger the extension, the more force is held within the band, therefore the more potential energy it will hold that can be converted to a larger amount of kinetic energy and a larger result of gravitational potential energy.

If we were to take the equation for calculating the gravitational potential energy,

GPE = m x g x h

We could then re-arrange it so that we could work out the change in height, as a possible indication to the heights we may achieve in the final experiment, for each read

h = GPE to work out the gpe:

m x g

Length of GPE = h = GPE PREDICTED HEIGHT

Extension 0.5 x height x base(of graph) m x g

(m) =0.5 x force x extension h

0.02cm 0.5 x 1.0 x 0.02 = 0.01 0.01J = 0.01 0.6m

0.0016kg x 10m/s 0.016

0.03cm 0.5 x 1.5 x 0.03 = 0.0225 0.0225J = 0.0225 1.4m

0.0016kg x 10m/s 0.016

0.04m 0.5 x 1.5 x 0.04 = 0.03 0.03J = 0.03 1.9m

0.0016kg x 10m/s 0.016

0.05m 0.5 x 2.2 x 0.05 = 0.055 0.055J = 0.055 3.4m

0.0016kg x 10m/s 0.016

0.06m 0.5 x 2.4 x 0.06 = 0.072 0.072J = 0.072 4.5m

0.0016kg x 10m/s 0.016

0.07m 0.5 x 2.7 x 0.07 = 0.0945 0.0945J = 0.0945 5.9m

0.0016kg x 10m/s 0.016

0.08m 0.5 x 2.8 x 0.08 = 0.112 0.112J = 0.112 7m

0.0016kg x 10m/s 0.016

We then carried out the final experiment, in the exact way of my method. The results were then recorded in a table, along side the predicted heights.

0.02 0.27 0.28 0.24 0.31 0.26 0.27m 0.6m

0.03 0.58 0.66 0.62 0.70 0.69 0.65m 1.4m

0.04 0.75 0.88 0.85 0.87 0.82 0.83m 1.9m

0.05 1.10 1.17 1.15 1.18 1.14 1m 3.4m

0.06 1.40 1.50 1.41 1.55 1.45 1.5m 4.5m

0.07 1.69 1.74 1.65 1.69 1.70 1.7m 5.9m

0.08 1.81 1.81 1.97 1.90 1.92 1.9m 7m