Materials

Question 1

Density

Answer 1

A measure of how closely packed particles are in a material

Defined as the mass per unit volume of a material

Question 2

Density equation

Answer 2

p=m/v

Kgm-³

Question 3

Whatever you do to the unit…

Answer 3

You do to the conversion factor

Question 4

Pico

Answer 4

-12

Question 5

Fempto

Answer 5

-15

Question 6

Measure mass

Answer 6

Balance

Question 7

Measure mass of liquid

Answer 7

Measure mass of container empty and full
With balance
Subtract to get mass of liquid
Read off volume on beaker
Density calculation

Question 8

Measuring irregular solid density

Answer 8

Measure mass with balance
Read off volume on beaker with and without object fully submerged in the water
Difference in volume is volume of solid
Density calculation

Question 9

If an objects density is less than the density of a fluid then

Answer 9

It will float

Question 10

Hooke’s law

Answer 10

The extension produced by a force in a wire or spring is directly proportional to the force applied
Up to the limit of proportionality

Question 11

Express Hookes law mathematically

Answer 11

F=kx

Question 12

Limit of proportionality

Answer 12

Point up to which Hookes law is obeyed in which force is directly proportional to extension
Point beyond which f and x stop being proportional

Question 13

Elastic limit

Answer 13

Not the same as the limit of proportionality
Occurs after limit of proportionality
Point beyond which a stretched spring won’t return to its original length

Question 14

When doesn’t a spring return to its original length

Answer 14

Beyond the elastic limit

Question 15

Gradient of force extension graph

Answer 15

Spring constant
Stiffness
Before limit of proportionality

Question 16

What is the spring constant

Answer 16

Measure of resistance to stretching

Stiffness

Question 17

Extension of springs in parallel

Spring constant

Answer 17

Stretch by half

Meaning spring constant has doubled

Question 18

Springs in parallel
Extension
Spring constant

Answer 18

Stretch twice as far

So spring constant halves

Question 19

Combined spring constant equation for series

Answer 19

1/ktotal = 1/k1 + 1/k2

Question 20

Combined spring constant for springs in parallel

Answer 20

Ktotal = K1 + K2

Question 21

Area under the graph of force extension

Answer 21

Work done on the spring

Since W=Fs and s=extension

Question 22

Explain the area under a force extension graph

Answer 22

Weight of masses stretches spring and does work on it
Increasing its elastic potential energy
So area gives elastic potential energy/strain energy stored stretching it to that point

In region before limit of proportionality area is a triangle
So can be calculated by doing 1/2 Fx

Question 23

Three equations to work out strain energy

Answer 23

E=1/2kx²

E=1/2F²/k

E=1/Fx

Question 24

Plastic deformation

Answer 24

Point in which an unloaded spring no longer returns to its original length when unloaded

Question 25

How do you work out the permenant extension

Answer 25

Draw a line from top of graph parallel to gradient of the region of proportionality Where it crosses x axis

Question 26

What is the difference in energy for the area loading and unloading

Answer 26

Energy used to permentantly deform the spring

Question 27

Elastic behaviour

Answer 27

Sample that has been deformed by a force returns to its original shape when the force is removed

Question 28

Elastic limit

Answer 28

Maximum force applied up to which a material can be stretched and return to its original shape

Question 29

Plastic behaviour

Answer 29

When the deforming force is removed and the material does not return to its original shape

Question 30

Ductile

Answer 30

Can be easily and permenantly stretched | Drawn out into wires

Question 31

Brittle

Answer 31

``` Cannot be permenantly stretched Will break soon after the elastic limit Tend to be very strong under compression But weak under tension Concrete Mortar Brick Stone ```

Question 32

Fracture

Answer 32

Point at which the material breaks due to the force applied

Question 33

Small plastic region

Answer 33

Brittle

Question 34

Large plastic region

Answer 34

Ductile

Question 35

Higher fracture point

Answer 35

Stronger material

Question 36

Steeper gradient

Answer 36

Stiffer material

Question 37

Special case rubber

Answer 37

Isn't really a Hookean region or limit of proportionality Gradient still represents spring constant But spring constant is constantly changing

Question 38

Difference in energy/area for rubber

Answer 38

Energy retained by the rubber as heat

Question 39

How does the graph of rubber show it doesn't obey Hookes law

Answer 39

No linear section to the graph | Where force is proportional to the extension

Question 40

What does spring constant depend on

Answer 40

Material | Dimensions

Question 41

A material will stretch ... if longer

Answer 41

More

Question 42

A material will stretch ... if its thicker

Answer 42

Less

Question 43

Why is youngs modulus better than spring constant

Answer 43

Isn't affected by materials dimensions Stress accounts for thickness Strain accounts for length

Question 44

Youngs modulus

Answer 44

Tensile stress/Tense strain

Question 45

Tensile stress

Answer 45

F/A

Question 46

Tensile strain

Answer 46

Change in length over original length | Ratio

Question 47

Youngs modulus terms

Answer 47

YM=Fl/A◇L

Question 48

Units for stress/YM

Answer 48

Nm-² | Pa

Question 49

Assumption with YM

Answer 49

Assume the cross sectional area is constant In reality the decrease in area is very small So say negligible

Question 50

Breaking stress

Answer 50

Stress at the fracture point

Question 51

Breaking strain

Answer 51

Strain at the fracture point

Question 52

Area under a stress strain graph

Answer 52

Area=Stress x Strain Area=F/A x ◇L/L (W=F◇L) A=W/AL So the work done per unit volume

Question 53

Can the energy equations be used for youngs modulus

Answer 53

Yes

Question 54

Breaking strain equation

Answer 54

Max extension/Origional length

Question 55

Breaking stress

Answer 55

Maximum force/Area

Question 56

True or false | A graph of stress against strain is always linear up to the elastic limit

Answer 56

False | Limit of proportionality

Question 57

True or false | If a material is stretched up to its elastic limit it will return to its original shape when released

Answer 57

True | Hasn't passed its elastic region which just means F and X aren't proportional