Young's Modulus

The diagram shows an extension - force diagram for a spring. Which of the following is correct?

• The gradient of this spring is about 0.5 N/cm.

• A stiffer spring has a steeper curve on this graph.

• A stiffer spring has a higher limit of proportionality.

• The curve shows that the spring has reached the limit of proportionality at 8 N.

An object is being stretched by force F, which depends on the length of the object, x. Which of the following expressions is always a correct expression for the work done, W? ('Δ' means a very small change in something)

Work W₀ is done in stretching a rubber band from its original length. How much elastic potential energy, E, is stored in the rubber band? (Another way to ask this question is, what is the maximum amount of work that can be done by the rubber band?)

• E < W₀

• E = W₀

• E > W₀

• It depends on the band.

What is a unit for stress?

• N

• N m^-1

• Pa

• no unit

Which of the following is a correct definition for strain?

• It is the length divided by the original length.

• It is the extension divided by the length.

• It is the extension divided by the original length.

• It is the force divided by the cross-sectional area.

Which of the following is not a correct statement about strain?

• It is a length divided by another length, so it has no unit.

• It is always larger than 1.

• It takes the same value for all objects made of the same material.

• It is equal to stress divided by Young's modulus.

What is not correct about the unit for Young's modulus?

• It has the same unit as stress.

• It has the same unit as stiffness.

• It has the same unit as pressure.

• It is equal to the unit of stress divided by the unit of strain.

Which of the following is the odd one out?

• Young's modulus

• mass density

• specific heat capacity

• electrical charge

Which of the following is a correct expression for the Young's modulus of a wire with a circular cross-section with diameter d? The original length, extension, and force are l, Δl, and F, respectively.

The diagram shows the stress - strain curve of a material sample. Which of the following is not true?

• The force - extension diagram of the sample will have a similar shape.

• The sample follows Hooke's law up to a stress of 400 MPa.

• The Young's modulus of the material is about 2×10⁵ Pa.

• The sample could be made from mild steel.