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# A Catapult Investigation.

Extracts from this document...

Introduction

Sanjayan Ravi         Page  of         5/2/2007

## Aim

The aim of this experiment is to investigate how far a piece of block would travel using a catapult with different weights on the block and different force applied to the catapult.

### Friction

I know from text books and from lessons that friction will affect how far certain object travels. Since I’m not going to change the friction or not going to change where I will do my experiment I don’t need to worry about this factor.

### Hypothesis

My hypothesis for this experiment is ‘the more force you apply to the rubber band the further the wood will travel but the more weight you put on the block of wood the less distance it’s going to cover.

### Apparatus

• A stool
• Rubber band
• Newton meter
• Weights
• A metre stick

### Method

I will do tests of 5, 10, 15 and 20 newtons force each with and without weights. I will put up to 3 weights on the block. I will do 5 repeats for each test.

Middle

28

3.2

Mean

5.6

Standard Deviation

0.80

### 5N+3Weight

 X (X-Mean) (X-Mean)^2 1 -1.6 2.56 2 -0.6 0.36 3 0.4 0.16 3 0.4 0.16 4 1.4 1.96 13 5.2 Mean 2.6 Standard Deviation 1.02

### 10N

 X (X-Mean) (X-Mean)^2 79 1.8 3.24 77 -0.2 0.04 76 -1.2 1.44 76 -1.2 1.44 78 0.8 0.64 386 6.8 Mean 77.2 Standard Deviation 1.17

### 10N+1Weight

 X (X-Mean) (X-Mean)^2 65 1 1 62 -2 4 59 -5 25 71 7 49 63 -1 1 320 80 Mean 64 Standard Deviation 4.00

### 10N+2Weight

 X (X-Mean) (X-Mean)^2 55 2.6 6.76 49 -3.4 11.56 58 5.6 31.36 53 0.6 0.36 47 -5.4 29.16 262 79.2 Mean 52.4 Standard Deviation 3.98

### 10N+3Weight

 X (X-Mean) (X-Mean)^2 38 -2.4 5.76 41 0.6 0.36 42 1.6 2.56 36 -4.4 19.36 45 4.6 21.16 202 49.2 Mean 40.4 Standard Deviation 3.14

### 15N

 X (X-Mean)

Conclusion

## Evaluation

I think that these results are not good because we didn’t check the elasticity of the rubber band.

### Elasticity of the rubber band

I know from the Internet that elasticity of a normal rubber band will change when you keep on stretching but there is a limit when the rubber band will not stretch further. I put 50g weight on a new rubber band and measured how much it stretched. I then took the weight and stretched the rubber band 20 times and put 50g weight and measured it. I did this until I got the same result 3 times. These are the results:

155mm

179mm

200mm

200mm

200mm

These results show that the elasticity of the rubber band will change but there is a limit to it. If I had done this and used the same rubber band then I can be sure that the results are not wrong. I think I collected enough results.

This student written piece of work is one of many that can be found in our GCSE Forces and Motion section.

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