Yr 12 - Behaviour of Materials

Question 1

Plastic Deformation

Answer 1

Irreversible deformation of a material.

Question 2

Elastic Deformation

Answer 2

Reversible deformation of a material.

Question 3

Stiffness

Answer 3

Extent to which an object resists deformation.

Question 4

Hookes Law

Answer 4

Extension is proportional to the force applied provided the limit of proportionality is not exceeded.

F = K x

Gradient = Force constant

Question 5

Force Constant

Answer 5

Amount of force required to produce an extension of one metre.

Question 6

Describe how to find information on a Force-Extension graph.

Answer 6

M (Gradient) = Spring Constant

Area (Under Graph) = Elastic Potential

Therefore, Ep = 1/2 f x

Question 7

Why does 1/2 appear on a Force-Extension graph?

Answer 7

Need to use Average force

• Average force = (Final Force - Initial Force) / 2
• Initial force = 0
• Therefore = 1/2 final force (Ep = 1/2 f x)

Question 8

What happens to the Force Constant in series.
And what is a series circuit.

Answer 8

1/Kt = 1/K1 + 1/K2 etc

(Components connected in a single path)

Question 9

What happens to the Force Constant in parallel.
And what is a parallel circuit.

Answer 9

Kt = K1 + K2 etc

(Current has multiple paths to flow)

Question 10

F ∝ x (In opposite direction to displacement)

Answer 10

?? Check with Sir

Question 11

Stress

Equation and unit

Answer 11

Force per unit cross-sectional area
(NM^-2).

Question 12

Strain

Equation and unit

Answer 12

Strain = Deformation of a material compared to its original length.
(No units)

Question 13

Youngs Modulus

Equation and unit

Answer 13

E = 𝛔 (Sigma) / ε (Epsilon)

• Measure of stiffness (Pa)

Question 14

Ultimate Tensile Strength (UTS)

Answer 14

Max stress before breaking.

Question 15

Elastic Limit

Answer 15

Max stress before irreversible deformation.

Question 16

Limit of Proportionality

Answer 16

Max stress where Stress ∝ Strain.

Question 17

Yield Point

Answer 17

Max stress before material becomes plastic.

Question 18

Elastic Region

Answer 18

Region where deformation reversible.

Question 19

Tough

Answer 19

Withstand large dynamic (moving) forces without breaking.

Question 20

Strong

Answer 20

Withstand large static (Non-moving) forces without breaking.

Question 21

Hard

Answer 21

Resistance to dents and scratches.

Question 22

Brittle

Answer 22

Little deformation before fracture.

Question 23

Ductile

Answer 23

Easily drawn into a wire.

Question 24

Polymeric

Answer 24

Stretches under a massive strain before breaking.

Question 25

Hysteresis loop

Answer 25

Lag between input and output due to a change in direction of force.

Question 26

Describe a Stress-Strain graph. (3)

Answer 26

• Hysteresis loop
• Area = Energy transferred / volume
• Grad = Youngs Modulus (Indicated Stiffness)

Question 27

What graph do you use to plot results from the Young Modulus experiment? (not completed)

Answer 27

• Extension - Tension (Mg)
• Grad = extension