Topic 4:Materials

Question 1

What is the equation for Density

Answer 1

P=M/V

Question 2

Define turbulent flow

Answer 2

where all parts of the fluid cross over into each other and don’t move in a parallel direction.

Question 3

Define laminar flow

Answer 3

Where all the parts of a fluid are flowing in the same direction(parallel direction)

Question 4

what are the features of Turbulent flow

Answer 4

Layers cross over
Produces swirls and eddies
Chaotic movement
Happens at high speeds
Non uniform

Question 5

What are the features of Laminar flow

Answer 5

Parallel Layers
Occurs at lower speeds
Streamline
Velocity is constant over time
uniform

Question 6

What does turbulent flow cause

Answer 6

Drag

Question 7

What is upthrust equal to

Answer 7

Weight of the fluid displaced

Question 8

Define viscosity

Answer 8

The measure of how resistant a fluid is to flowing

Question 9

What happens to viscosity when heat increases

Answer 9

When heat of a liquid increases viscosity decreases

Question 10

What happens to velocity when viscosity increases

Answer 10

The higher the viscosity the more slowly a liquid flows

+viscosity = - velocity

Question 11

Define drag

Answer 11

The forces that oppose the motion of an object moving through a fluid (gas or liquid)

Question 12

What is the equation for stokes law

Answer 12

F=6πrηV

Question 13

Derive the equation for terminal velocity on a spherical object falling downwards

Answer 13

weight =upthrust +Drag

P=M/V so M=P x V

W=MxG
so W=P x V x G
W=Ps x 4/3πr^3 x G

Upthrust= weight of fluid displaced

Weight of fluid displaced = volume of object
V=4/3πr^3
U=4/3πr^3
W=U so
U= Pf x 4/3πr^3 x G

stokes law 6πrηV

W=U+D(stokes law)

Ps x 4/3πr^3 x G = Pf x 4/3πr^3 x G + 6πrηV
(Cancel πr)
(- Pf x 4/3r^2)
then collect like terms
4/3r^2g(Ps–Pf)=6ηV

V=4/3r^2g(Ps–Pf)/6η

V=2/9r^2g(Ps–Pf)/η

Question 14

Which way does drag act on a falling object

Answer 14

upwards

Question 15

what is the volume of a sphere

Answer 15

4/3πr^3

Question 16

which way does drag act on a rising object

Answer 16

downwards

Question 17

Define Hooke’s law

Answer 17

The force applied to a spring is directly proportional to its extension

Question 18

what is weight equal to as a spherical object falls through a liquid at a terminal velocity an the forces are balanced

Answer 18

Weight=upthrust+stokes law

Question 19

What is the equation for Hooke’s law

Answer 19

F=KE

Question 20

Define Elastic deformation

Answer 20

When an object can compressed/Stretched and returns back to its original shape

Question 21

Define Inelastic deformation

Answer 21

When an object can compressed/Stretched but doesn’t return back to its original shape

Question 22

What is the Equation for elastic potential energy

Answer 22

EPE=1/2K x X^2

Question 23

How do you find energy from a Force/Extension graph

Answer 23

Finding the area under the graph using the equation
1/2 FxE

Question 24

What is the gradient of a force extension graph

Answer 24

Spring constant

Question 25

Define spring constant

Answer 25

Stiffness(how easy or hard it is to stretch)

Question 26

In a force extension graph define the Elastic Plastic and fracture stages

Answer 26

Elastic= the point where the object will deform and return to its original shape Plastic= the point where the object will continue deforming with added force, not returning back to its original shape Fracture=The point where the object breaks

Question 27

Define stress

Answer 27

Force per unit of a cross sectional area

Question 28

Define strain

Answer 28

Extension per unit length

Question 29

What is the equation for Stress

Answer 29

σ=Force/Area

Question 30

What is the equation for Strain

Answer 30

ε=Extension/Length

Question 31

What is young modulus

Answer 31

The ratio between stress and strain

Question 32

what is the Equation for young modulus

Answer 32

Stress/ Strain Force/area _____________ Extension/length Force x length ___________ Area x extension

Question 33

Whats another way to write young modulus

Answer 33

Fx/AΔx

Question 34

What is the unit for young modulus

Answer 34

Nm^-2

Question 35

What is the gradient of a stress strain graph

Answer 35

Young modulus

Question 36

What is the Elastic limit

Answer 36

beyond this, the material is permanently deformed & wont return to its original shape

Question 37

What is the limit of proportionality

Answer 37

From this region onwards the metal can still behave elastically but cannot be relied upon to do so

Question 38

What is Yield point

Answer 38

Beyond this point material undergoes a sudden increase in extension(as the atoms reorganise themselves significantly)

Question 39

What is the Breaking/fracture stress

Answer 39

The stress Which causes the material to break.

Question 40

What is the ultimate Tensile Stress

Answer 40

The highest value of stress the material can ever attain

Question 41

Define stokes law

Answer 41

A way to calculate viscous drag

Question 42

Define viscous drag

Answer 42

Viscous drag is The friction between the surface of a object and a fluid as it the object moves through the fluid

Question 43

what is the equation for work done

Answer 43

W=force x displacement/distance