*Question*

An object is stretched until it reaches the elastic limit.

Which statement must describe the stress on the object when it is at the elastic limit?

**A** It is the maximum stress for which the object obeys Hooke’s law.

**B** It is the maximum stress that can be applied to the object before it has elastic deformation.

**C** It is the maximum stress that can be applied to the object before it has plastic deformation.

**D** It is the maximum stress the object can withstand before it breaks.

**Answer/Explanation**

Ans:

### Question

Two identical springs are connected in parallel. A weight of 8.0 N is hung from the combination, as shown.

The graph shows the variation with length of the force applied to **one** of the springs. What is the strain energy in **one** of the springs?

**A** 0.060J **B** 0.12 J **C** 0.14 J **D** 0.24 J

**Answer/Explanation**

Ans :

### Question

Forces are applied to the ends of a rod so that its length increases. The variation with force *F* of

the extension e of the rod is shown.

The point P is the elastic limit.

Which shaded area represents the work done during the plastic deformation of the rod?

**Answer/Explanation**

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**Question**

**Question**

An unstretched rubber cord is stretched by a force. The force F is plotted against the extension x.

F is slowly increased from zero, causing the cord to extend along path P. F is then reduced back

to zero along path Q.

What is represented by the shaded area?

A the elastic energy stored in the rubber cord

B the energy that causes plastic deformation

C the energy dissipated as heat

D the work done to extend the rubber cord

**Answer/Explanation**

### Question

A wire is stretched by applying increasing values of force F. For each value of force applied, the

extension x is recorded. A force–extension graph is plotted from the data obtained.

Which statement about the area under the graph **must** be correct?

**A** It can be calculated as ½ Fx .

**B** It is the elastic potential energy stored in the stretched sample.

**C** It is the work done in stretching the sample.

**D** It would be the same for any wire of the same material.

**Answer/Explanation**

Ans