Spring Investigation

normal position.

. Do the above for each spring making sure you record it to the nearest millimetre.

Measurements

I will be using, 10g masses to extend the springs, a 1metre stick to record the

extension, and 5 nichrome springs with a gauge of 20swg, 24swg, 28swg, 32swg, and

36swg to extend.

Observations

I will make sure it is a fair test by accounting for all the factors that will affect the

stretching of the spring.

. Type of wire

. Size of the load

. Length of wire

. Cross-sectional area of the wire

. Metal type

. Number of coils

. temperature

Some of these will have more of an effect than others on the results, e.g. Type of

wire and temperature. The type of wire will have more of an effect on the results then the

temperature would because the wire could be very brittle or very flexible so the stretching of

it would be different, whereas if the temperature dropped a few degrees there wouldn't be a

very big difference. We will keep the same type of wire (nichrome), the same length of wire

(1m) and the same diameter of the spring (5mm). We will change the cross-sectional area of

the wire. There will be five different thickness', 20swg, 24swg, 28swg, 32swg and 36swg.

I am going to record the extension of the springs until they go past the elastic region

into the plastic region. This is where the springs won't return back to their original position

because they are over stretched.

I am not going to record outside the plastic region because Hooke's Law is not

obeyed and Hooke's Law is what I have based my prediction on.

The results will be fairly accurate as I will measure to the nearest millimetre.

Apparatus

* Clamp stand: To hold the spring and the metre stick.

* Metre stick: To record the results.

* 5 springs: To carry out the investigation with.

* 10g masses: To extend the springs.

Plan of action

First of all we set up the equipment as shown in the diagram, then we made the

springs by wrapping all of the five different widths of Nichrome wire round a core of five

millimetres each with a hook at both ends.

Starting with the 20swg we hooked it onto the clamp stand and lined the metre stick

up with the bottom of the spring at 200 millimetres so it would be easier to record the

results.

Once we had done all the above we started to add on the 10g masses one by one

until the spring went past the elastic region. We did this with each wire recording the

extension to the nearest millimetre every time a 10g mass was added.

Fair test

To make this a fair test I will ensure that each gauge of wire is a metre long, that I

record the results to the nearest millimetre and that I use the same diameter for each spring.

Swg

Newtons

(N)

Reading

(mm)

Total extension

(cm)

36

0

0.1

0.2

Went past the elastic limit

200

905

962

0

705

762

32

0

0.1

0.2

0.3

Went past the elastic limit

200

278

410

505

0

78

210

305

28

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

.0

.1

Went past the elastic limit

200

215

220

239

250

265

288

295

320

349

415

427

0

5

20

39

50

65

88

95

20

49

215

227

24

0

2

3

4

5

6

Went past the elastic limit

200

220

235

292

322

463

677

0

20

35

92

22

263

477

20

0

2

3

4

5

6

7

8

9

0

1

2

3

4

5

6

7

At this point the hook gave way.

200

200

205

205

207

214

225

228

252

256

257

260

264

270

273

280

290

315

0

0

5

5

7

4

25

28

52

56

57

60

64

70

73

80

90

15

Evaluation

Overall the experiment went well, the results are reliable but not accurate. The

reasons for this are:

* Hooks: each hook made was a different size, therefore the wire will have changed in

length resulting in a shorter or longer spring which would then affect the results.

* Thickness of wire: the thicker the wire the less coils there will be because if it's thicker it

will take up more wire to wrap it round the diameter of the coil.

* Uneven coils: I noticed on one of the springs that it started to over stretch in the middle,

so the figures cannot necessarily be relied upon though the pattern of heavier weight on

thicker wire is as expected.

* Hooks giving way: this stopped me from recording fully what the final results would have

been.

All of these affected the overall results, but from the graph it shows the theory of

Hooke's Law clearly.

The method that I used was a good outline of what would give me accuracy but I

did not include all of the little details. To improve the method I should have detailed it more

with the little things that make a big difference.(The above)

I did not repeat any of the results but I found that there were two anomalous results

both from the same spring but the rest all seemed to fit in with the Hooke's Law theory.

To get a better set of results I could have made the test a lot more fair, for example:

extra length for the hook, measure the extension of the spring with an object instead of by

eye, even up the coils on each spring taking care that there are no gaps.

To extend this particular investigation I could repeat the experiment with a variety of

metals. The different metals would probably have a different extension with the same

weight. A use of this would be that different metals would be more suitable for different

tasks whether as individual components or as part of a working machine.

Conclusion

I have concluded that the thickness of the wire does affect the stretching of a spring.

Therefore the thicker the wire the larger the mass has to be for it to extend then a thinner

wire.

Diagrams

The diagrams above show the stretching of a spring when in the elastic region. The

molecules slip and slide over each other as the weight is applied, this causes the spring to

extend. As the weights are taken off the molecules slide back to their original position.

However when the spring enters the plastic region by an increase in the load it produces a

much bigger extension then before. This causes internal slipping to take place between the

layers of atoms and is called plastic deformation. The spring will not return to its original

position.