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# To investigate the behaviour ofan elastic material when a tensile force is applied.

Extracts from this document...

Introduction

## Sian Jones 11BGC

Aim: To investigate the behaviour of an elastic material when a tensile force is applied.

What I know: In the 1660s Robert Hooke investigated how springs and wires stretched when loads were applied. He found out that for many materials, the extension and load were in proportion provided the elastic limit was not exceeded.

Materials can be compressed as well as stretched. If a material is stretched but springs back to its original shape they are known as elastic. However they stop being elastic if bent or stretched too far. They either break or become permanently deformed.

The springs represent the bonds caused by the forces of attraction and repulsion between the atoms, due to the electric charges of their nuclei and electrons.

The attractive forces between the molecules in a solid provide its characteristic elastic or stretchy properties. When we stretch a solid, we are slightly increasing the spacing of it molecules.

The tension we can feel in a stretched spring is due to all the forces of attraction between the molecule in the spring.

Possible variables: I could change

• Material of spring
• Length of spring

Variables I will study: I will study the mass of load.

How I will make my test fair and why:

Middle

I measured the length of the spring to the nearest millimetre using a ruler.I marked a line on the ruler for the length of the spring with ought any mass on it.I added a 100g weight onto the spring. I calculated the extension of the spring by subtracting the initial length reading for the unloaded spring form the loaded spring.I then calculated the stretching force which was the mass X N/Kg. The 10N/Kg being the pull of gravity.I then calculated the constant which was done using the formula;

## Stretching force / extension

1. I then took the weight off the spring and measured it again using a ruler to see if there was any deformation to the spring.
2. I then repeated the method until the spring was deformed and would not return to its original state.

Results table:

### Mass

(g)

100 g

200 g

300 g

400 g

500 g

600 g

700 g

800 g

900 g

1000 g

1100 g

1200 g

1300 g

Extension

(mm)

37 mm

77 mm

116 mm

170 mm

224 mm

268 mm

285 mm

335 mm

382 mm

408 mm

489 mm

511 mm

591 mm

Stretching force

Conclusion

However the masse that were added on each time (+ 100g) were very reliable as I used a correct weights.

The spring I used was also kept separately from the other springs. This is because using a new spring would effect the results, as the one we started to use would begin to deform.

I think that my method was suitable, because I set up the apparatus and collected all the things I needed before starting the investigation.

I also measured the extension and the deformation in a correct order that suited my experiments.

My measurements were as accurate and reliable as I could make them using the apparatus I had. I made sure that every individual weight was done correctly.

To improve my investigation for next time, in order to get more evidence for my conclusion I will do a number of things.

1. Make sure that a splint is used for all the individual mass
2. Measure the extension and deformation more accurately using a more reliably measuring device.
3. I will repeat the investigation in order to collect more results.
4. Investigate other elastic and plastic materials to see if there is any relationship between their extension and stretching force. I will then be able to comment on the elastic limit of different materials.
5. I could use different length springs.
6. Use smaller weights so I can get a more accurate reading of its elastic limit.

This student written piece of work is one of many that can be found in our AS and A Level Waves & Cosmology section.

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