Materials

Question 1

What is Archimedes’ principle

Answer 1

• Upthrust magnitude=weight of fluid displaced by the body

Question 2

What is upthrust

Answer 2

• When a body is fully or partially submerged in a fluid, pressure differences at different depths cause it to experience an upward force- upthrust

Question 3

What is laminar flow

Answer 3

• Flow in layers

Question 4

Characteristics of laminar flow

Answer 4

• Occurs at lower speeds and around streamlined objects
• Layers do not mix and are roughly parallel to each other

Question 5

What happens in turbulent flow

Answer 5

• Flow is chaotic and subject to sudden change in speed and direction
• Large scale mixing of fluid layers

Question 6

What are streamlines

Answer 6

• Lines of laminar flow
• At any point in each of these streamlines the velocity with time of the flow will be constant

Question 7

What is viscous drag on objects

Answer 7

• The frictional force between layers of fluid being present when a solid moves through a liquid

Question 8

When is viscous drag largest

Answer 8

• In turbulent flow rather than laminar flow

Question 9

What does stokes law equation give us

Answer 9

• Formula for viscous drag for small spheres at low speeds in laminar flow

Question 10

What is Hooke’s law

Answer 10

The force needed to extend a spring is proportional to the extension of the spring

Question 11

When is Hooke’s law obeyed

Answer 11

• If material has not passed its limit of proportionality

Question 12

What is Hooke’s law equation

Answer 12

Force=stiffness x extension

Question 13

What is distortion

Answer 13

• A change in shape of an object

Question 14

What is elastic distortion

Answer 14

• Temporary distortion- will go back to its original shape

Question 15

What is inelastic/plastic distortion

Answer 15

• permanent distortion- will not go back to original shape

Question 16

What is the elastic limit

Answer 16

• The maximum force a body can endure and still regain original shape and size

Question 17

What is the limit of proportionality

Answer 17

The point where Hooke’s law ceases to be obeyed

Question 18

What is elasticity

Answer 18

• The property a material has whereby it regains its original size and shape when a deforming force is removed

Question 19

What is stiffness

Answer 19

• A measure of a body’s resistance to changes in size/shape

Question 20

What is a yield point

Answer 20

• When a large extension is produced for a very small increase in force
• The material of the body is said to show ‘plastic’ behaviour

Question 21

When do stress and strain occur

Answer 21

When forces deform an object it is said to be STRESSED. As a result the material becomes STRAINED

Question 22

What is stress

Answer 22

• The force per unit area acting on a material

Question 23

What is strain

Answer 23

The extension per unit original length

Question 24

What is young modulus

Answer 24

The measure of the ability of a material to withstand changes in length with an added load

Question 25

What is the ultimate tensile stress/ultimate strength

Answer 25

Th highest value of stress attained in the material

Question 26

What is the fracture/breaking stress

Answer 26

The value of stress in the material when the sample breaks

Question 27

What is the area under the graph of a stress/strain graph equal to

Answer 27

Energy stored per unit volume

Question 28

What is strength

Answer 28

- A measurement of how much a material resists stress/deformation - A strong material has a high breaking stress

Question 29

What is ductility

Answer 29

- A property that allows materials to be drawn into a wire, because it can be pulled without breaking due to layers of atoms able to slide over each other

Question 30

What is malleability

Answer 30

- A property that allows a material to be hammered/pressed into shape when it experiences compressive stress - Atoms in layers and can slide over each other

Question 31

What is creep

Answer 31

A permanent deformation that increases slowly with time due to constant mechanical stress

Question 32

How to identify stiff object

Answer 32

- Steep gradient on force extension graph - High young modulus

Question 33

What is toughness

Answer 33

- High energy density up to a fracture

Question 34

What is hardness

Answer 34

- Difficult to indent the surface

Question 35

What is elastic strain energy

Answer 35

- The energy stored in the material due to the work being done on the material in stretching it