Chapter 6 - Materials

Question 1

Define Tensile Stress.

Answer 1

Tensile Stress = Force ÷ Cross Sectional Area

𝜎 = F/A

Question 2

Define Tensile Strain.

Answer 2

Tensile Strain = Extension / Original Length

ε = x / L

Question 3

Define Young’s Modulus.

Answer 3

Question 4

Define Hooke’s Law.

Answer 4

Hooke’s Law states: The extension of the spring is directly proportional to the force applied.

F ∝ x
Force is directly proportional to extension.
F = kx
Force = Force Constant (or stiffness) x extension
N = Nm⁻¹ x m

Question 5

What is the area under a force-extension graph equivalent to?

Answer 5

The area under a force-extension graph = work done.

Question 6

Define Elastic Potential Energy.

Answer 6

Elastic Potential Energy is defined as:

E = 1/2 Fx 
Energy = 1/2 x Force x Extension
J = 1/2 x N x m

OR

E = 1/2 kx²
Energy = 1/2 x Force Constant x Extension²
J = 1/2 x Nm⁻¹ x m²

Question 7

What is shape that is formed by a rubber force-extension graph.

Answer 7

The shape that is formed by a rubber force-extension graph is called a hysteresis loop.

Question 8

What is the difference in extension for springs in parallel vs in series?

Answer 8

For Parallel Springs: The extension is equal for identical springs, meaning the force is distributed over the springs. E.G for two identical springs, each of them experiences 1/2 of the force.

For Series: The extensions of the two springs is added together, meaning each spring experiences the full force. E.G for two identical springs, they both extend as much as they would when individually acted on by that force.

Question 9

Define Tensile Force.

Answer 9

Forces that produce extension are known as tensile forces.

Question 10

Describe a force extension graph in terms of extension, elastic limit, and the two different types of deformation.

Answer 10

Question 11

Describe this stress-strain graph.

Answer 11