# D2 Measurong Young's modulus of copper(TAS)

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Introduction

D2 Measurong Young's modulus of copper(TAS)

Objective

In this experiment, The Young's modulus of copper will be mesured .

Apparatus

- copper wire 4m

- G-clamp

- polley on clamp

-2*Wooden block

- 2*rule (half meter and meter rule)

- slotted mass with hanger 15 * 0.1 kg

- adhesive label

-micrometer screw gauge

-safety goggles

-polystyrene board

(Warning : Wear safety goggles when doing this experiment )

Theory

When a spring is stretched or compressed by a force.The extension is directly proportional to the applied force.This relationship known as Hooke's law.

Force=ke.However,the law is used when the proportional limit is not exceeded.To further investigate how the material behaves when it is stressed,we define:

The stress applied to the wire is defined as the force applied per unit cross-sectional area.

Stress = force per unit area =F/A

(where F is the force or tension in the wire, A is the cross-sectional area)

When the wire being stretched,it is under strain.The strain is defined as the extension per unit length.

Middle

3rd measurement

Diameter d/m

0.00028

0.00028

0.000275

Mean diameter of wire d = 0.000278 m

Original length of wire l = 3.95 m

Load m/kg | 0 | 0.1 | 0.2 | 0.3 | 0.4 | 0.5 | 0.6 |

Extension e/m | 0 | 0.001 | 0.002 | 0.0025 | 0.0028 | 0.003 | 0.0038 |

0.7 | 0.8 | 0.9 | 1.0 | 1.1 | 1.2 | 1.3 | 1.4 | |

0.0042 | 0.005 | 0.007 | 0.009 | 0.015 | 0.036 | 0.087 | 0.155 |

Before the load increase to 0.7 kg.The extension is nearly proportional to the force .Also stress is nearly proprtional to strain.After the load is beyond 0.7kg,extension is not proportional to force and stree is not proportional to strain.The plastic deformation occur.The wire does not return completely to its original length .The wire broke whn the load is increase to 1.4 kg.

This part of graph obeys Hooke’s law.

Fig. 4

% strain = extension / original length x 100%

= 0.0042/ 3.95x 100%

= 0.106%

Fig.

Conclusion

Young's modulus is more useful than force constant because the Young's modulus depend on the force per unit cross sectional area.Also,the extension is per unit length.It is more accuracy than the force constant which is only depend on the relationship between the force and extension.

From the book called NEW WAY PHYSICS.the young's modulus of the copper is 124x109 Pa.

Also from http://www.answers.com/topic/young-s-modulus.

the Young's modulus is between110 to 130 x109 Pa.

Compare with our result.It is 124x109 Pa.The answer is very close to the reference answer.It is because we take all of the value very carefullyand seriously for decrease the error.

Conclusion

The Young's modulus is depend on the materials.The Young modulus of copper which measure by our group is 124x109 Pa

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

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