2. Materials

Question 1

Force on a spring equation

Answer 1

Force = spring constant (k) x extension

Question 2

What does a larger spring constant mean

Answer 2

The spring is stiffer

Question 3

Equation for stress

Answer 3

Stress = Force / Area

Question 4

Equation for strain

Answer 4

Strain = extension / original length

Question 5

Youngs modulus equation

Answer 5

Stress / strain

Question 6

What are the conditions to calculate youngs modulus

Answer 6

That the material is obeying hookes law

Question 7

What does the area under a force extension graph represent

Answer 7

The work done

Question 8

If a material has gone over the limit of elasticity then what happens

Answer 8

It will not return to its original shape or length

Question 9

Equation for Elastic Potential Energy

Answer 9

EPE = 1/2 x k x X^2
EPE = 1/2 x F x X

Question 10

What are the three classifications of solids

Answer 10

Crystalline
Amorphous
Polymeric

Question 11

What are the properties of a crystalline material

Answer 11

Ductile
Tough
Made from a lattice structure

Question 12

What are the properties for an Amorphous structure

Answer 12

This has a non ordered structure
Rigid
Strong

Question 13

What are the properties of a Polymeric structure

Answer 13

Long chained polymers
Strong
Flexible

Question 14

Give an example of a Crystalline structure

Answer 14

Diamonds, Sugar, Most metals

Question 15

Give an example of an amorphous structure

Answer 15

Glass or ceramics

Question 16

Give an example of a polymeric structure

Answer 16

Plastics, Clothing and Meats

Question 17

Define necking

Answer 17

When the cross sectional area of a material becomes so small that it deforms plastically and could create a ductile fracture at that point

Question 18

What are edge dislocations

Answer 18

When crystalline structures are put under strain the gaps in between atoms allow a row of to slip out of formation, spreading the dislocation throughout the metal. This makes it much weaker

Question 19

How can you prevent or reduce the effects of edge dislocation

Answer 19

Create a compound of different metals which introduces different sized atoms into the structure which stops edge dislocation from spreading.

Question 20

What does introducing more grain boundaries do to a metal

Answer 20

This means that there are more boundaries so then edge dislocation is more contained and cannot spread in the metal

Question 21

What causes brittle fractures

Answer 21

Crack Propagations

Question 22

What is crack propagations

Answer 22

When small imperfections in the surface of a metal come under stress the cracks become bigger until it fractures open

Question 23

What do the imperfections on a metal decrease

Answer 23

The breaking stress of a material

Question 24

What does a graph of a brittle material look like

Answer 24

They have a steep gradient so a large young modulus
But also they are not strong so they fracture before they can stretch further

Question 25

What does a graph of a rubber material look like

Answer 25

It creates a hysteresis graph meaning the loading curve is above the unloading curve

Question 26

What does the area on a hysteresis graph represent

Answer 26

The energy per unit volume stored as thermal energy

Question 27

Does a rubber material have a low or high youngs modulus

Answer 27

Very low as it isnt a stiff material

Question 28

What happens to rubber materials when it is overloaded

Answer 28

The rubber then cannot return back to its original form or breaks