4+5 Revision

Question 1

What is Hooke’s law?

Answer 1

Extension is proportional to force (when elastic limit is not exceeded)
F=Kx

Question 2

In Hooke’s law what is k?

Answer 2

The spring constant/stiffness

Question 3

In Hooke’s law what is x?

Answer 3

The extension

Question 4

What happens to the spring constant in series?

Answer 4

1/kt=1/k1+1/k2+1/k3…

Question 5

What happens to the spring constant in parallel?

Answer 5

k=k1+k2+k3

Question 6

What are the four kinds of deformation?

Answer 6

tension, compression, torsion, shear

Question 7

In an F/X graph what is the area under the graph?

Answer 7

The work done to stretch the object

Question 8

What is the formula for elastic potential energy?

Answer 8

PE=1/2kX^2

Question 9

Is the young modulus an object or material property?

Answer 9

material

Question 10

What is the area under a stress v strain graph?

Answer 10

The energy absorbed per unit volume

Question 11

What is the structure of MOST materials?

Answer 11

crystalline

Question 12

What is a crystalline structure?

Answer 12

A regularly repeating pattern of atoms or ions

Question 13

What structure do polymers have?

Answer 13

Can be either crystalline or amorphous

Question 14

What is an amorphous structure?

Answer 14

Irregular, jumbled structure

Question 15

Name two amorphous materials

Answer 15

Cross linked rubber

Glasses

Question 16

What four things give evidence of the size of an atom?

Answer 16

• Rayleigh’s oil drop experiments
• X-ray diffraction
• modern electron microscopes
• Atomic force or tunneling microscopes

Question 17

What is the size of one atom?

Answer 17

about 0.5*10^-9m

Question 18

In theoretical perfect structures what stress is needed for a whole plain of atoms to slip?

Answer 18

roughly E/3 Pa

Question 19

In actual structures what stress is needed to move a whole plane of atoms?

Answer 19

roughly E/1000 Pa

Question 20

What are dislocations?

Answer 20

Essentially an extra half plane of atoms

Question 21

How can metallurgy be used to control the properties of materials?

Answer 21

• alloying
• thermal treatments
• mechanical deformation

Question 22

How does alloying affect material properties?

Answer 22

Foreign atoms obstruct dislocation movement to raise the yield stress

Question 23

How do thermal treatments affect the properties of metals?

Answer 23

It makes precipitates and modifies the number and mobility of dislocations

Question 24

How does mechanical deformation affect the mechanical properties of metals?

Answer 24

Dislocations multiply and become entangled

Question 25

What is annealing?

Answer 25

Heating to a very high temperature

Causes more plastic deformation (easier to shape)

Question 26

What is quenching?

Answer 26

cooling very fast after heating to very high temperatures

makes material very brittle

Question 27

What is tempering?

Answer 27

Heating with a lower flame and then cooling slowly

Original properties should be recovered