4 Materials

Question 1

Equation for density

Answer 1

p=m/v

Density=mass/volume

Question 2

Equation for pressure in a fluid (learn)

Answer 2

P=hpg

Pressure=height x density x gravity

Question 3

What is upthrust equal to?

Answer 3

The weight of the fluid displaced

U= mg of fluid displaced

Question 4

Cohesive

Answer 4

Forces of neighbouring molecules in the fluid

Question 5

Adhesive

Answer 5

Forces of the surfaces of solids (obstacles/walls of pipe)

Question 6

Laminar

Answer 6

When particles don’t cross over each other (streamlined)

Question 7

Turbulent

Answer 7

When particles do cross over each other

Question 8

Eddy currents/ vortices

Answer 8

When the fluid swirls around and is turbulent

Question 9

When can Stokes law be used?

Answer 9

When a small spherical ball is falling through a fluid in which the flow of the fluid is laminar

Question 10

Stokes law

Answer 10

F=6 x pi x n x r x v

F=viscous drag
n=the coefficient of viscosity
r=radius of sphere
v= velocity

Question 11

Hookes law

Answer 11

k= F/x

Question 12

Limit of proportionality

Answer 12

The point where hookes law ceases to be obeyed

Question 13

Elastic limit

Answer 13

When the load is removed, spring will no longer take original shape

Question 14

Yield point

Answer 14

The onset of plastic flow

Question 15

Elastic behaviour

Answer 15

When a force is exerted the bonds holding the atoms together are stretched

Question 16

Plastic flow

Answer 16

When a force is exerted the layers of atoms slide over each other and can’t return

Question 17

What happens to polymers when a force is applied?

Answer 17

Polymers have long chain molecules which are tangled. When a force is applied they untangle and there is a large extension. Then the bond becomes harder to stretch once they are untangled

Question 18

Young’s modulus

Answer 18

E=stress/strain

Question 19

Equation for stress

Answer 19

Stress= force/area

Question 20

Equation for strain

Answer 20

Strain= extension/ original length

Question 21

What is true when stress strain graphs are proportional?

Answer 21

The gradient is proportional

Question 22

Strong

Answer 22

High breaking stress

Question 23

Hardness

Answer 23

How difficult it is to indent the surface

Question 24

Stiffness

Answer 24

The gradient of a force extension graph

Question 25

Toughness

Answer 25

The energy density up to fracturing

Question 26

Elastic

Answer 26

Regains original shape when force is removed

Question 27

Ductile

Answer 27

Can be drawn into wires

Question 28

Malleable

Answer 28

Can be hammered into thin sheets

Question 29

Elastic strain energy

Answer 29

Elastic strain energy= force x extension

Question 30

How can elastic strain energy be found on a force extension graph

Answer 30

Area under graph

A=1/2Fx

A=1/2kx^2

Question 31

What is the gap between the loading and unloading curve in a hysteresis in rubber?

Answer 31

Energy lost as thermal energy

Question 32

Strength

Answer 32

Stress needed to break

Question 33

With reference to the stress strain graph, why are ductile materials suitable for the production of wires

Answer 33

They have a large region of plastic deformation