Sress, Strain and Young Modulus

Pick the suitable units for stress?

• N/m

• N/m²

• Nm

• Nm²

A 5m wire experience a strain of 8%. What is the extension of the wire?

• 1.6 m

• 0.4 m

• 0.04 m

• 0.016 m

Pick the suitable units for Young's Modulus?

• N/m

• N/m²

• Nm

• Nm²

A sample of wire has a Young modulus E. A second sample of wire made from an identical material has three times the length and half the diameter of the first sample.

What is the Young modulus of the second sample of wire in terms of E?

• E

• 0.5 E

• 2 E

• 0.25 E

A steel wire has a cross-sectional area 0.5 mm². The Young modulus of steel is 2.0 × 10¹¹ Pa. Assume the wire obeys Hooke’s law.

What load must be suspended from the wire to produce an extension which is 0.1% of the original length?

• 200 N

• 100 N

• 50 N

• 40 N

The diagram shows how the stress varies with strain for metal specimens X and Y which are different. Both specimens were stretched until they broke.

Which of the following is incorrect?

• X is stiffer than Y

• X has a higher value of the Young modulus

• X is more brittle than Y

• Y has a lower maximum tensile stress than X

What is the Youngs Modulus if a stress of 25MPa causes a strain of 0.3%?

• 8x10⁹ Pa

• 8x10⁶ Pa

• 8x10³ Pa

• 8x10^-3 Pa

A steel wire W has a length l and a circular cross-section of radius r. When W hangs vertically and a load is attached to the bottom end, it extends by e.

Another wire X made from the same material has the same load attached to it.

Which length and radius for X will produce an extension of e/4 ?

• A

• B

• C

• D

Look at the picture!

• A

• B

• C

• D

In stress-strain experiments on metal wires, the stress axis is often marked in units of 10⁸ Pa and the strain axis is marked as a percentage. This is shown for a particular wire in the diagram