Chapter 9

The diagram shows a beam supported on two pivots. Which statement describes the state of the top surface X and of the bottom surface Y?

• Both X and Y are in compression.

• Both X and Y are in tension.

• X is in compression and Y is in tension.

• X is in tension and Y is in compression.

A number of identical springs are joined in four arrangements.

Which arrangement has the same spring constant as a single spring?

• A

• B

• C

• D

The diagram shows the force-extension graph for a sample of material. The sample is stretched and then returns to its original length. Which area represents the work done to stretch the sample?

• P + Q

• P only

• Q + R

• R only

A sample of material is stretched by a tensile force to a point beyond its elastic limit. The tensile force is then reduced to zero.

Which area represents the net work done on the sample?

• X

• X + Y

• Y + Z

• Z

The Young modulus of a metal is determined by stretching it elastically. This can be done by making measurements when loads are added to a wire. Which measurements are needed to calculate the stress and strain of the wire in such an experiment?

• A

• B

• C

• D

The diagram shows the stress-strain graph for bone.

What is the Young modulus of bone?

• 1 × 10⁶ N m^–2

• 2 × 10⁶ N m^–2

• 1 × 10⁸ N m^–2

• 2 × 10⁸ N m^–2

A steel bar of circular cross-section is under tension T, as shown.

The diameter of the wide portion is double the diameter of the narrow portion.

What is the value of (stress in the wide portion)/(stress in the narrow portion)?

• 0.25

• 0.50

• 2.0

• 4.0

The Young modulus of steel is determined using a length of steel wire and is found to have the value E.

Another experiment is carried out using a wire of the same steel, but of half the length and half the diameter.

Which value is obtained for the Young modulus in the second experiment?

• 0.5 E

• E

• 2 E

• 4 E

Which statement about elastic and plastic deformation is correct?

• Elastic deformation and plastic deformation are proportional to the applied force.

• Elastic deformation and plastic deformation cause no change in volume.

• Elastic deformation causes heating of the material but plastic deformation does not.

• Elastic deformation is reversible but plastic deformation is not.

A sample of metal is subjected to a force which increases to a maximum value and then decreases back to zero.

When the sample contracts it follows the same force-extension curve as when it was being stretched.

What is the behavior of the metal between X and Y?

• both elastic and plastic

• not elastic and not plastic

• plastic but not elastic

• elastic but not plastic