Materials

Question 1

Density equation

Answer 1

Density = mass/volume

Question 2

Density definition

Answer 2

The mass per unit volume

Question 3

Density unit

Answer 3

Kg/m^3

Question 4

How is the density of a regular solid measured

Answer 4

Measure the mass using a top pan balance, measure its dimensions using vernier calipers or a micrometer and calculate its volume using the appropriate equation,

Question 5

How’s the density of a liquid measured

Answer 5

Measure the mass of an empty measuring cylinder, pour the liquid into a measuring cylinder and measure the volume directly. Measure the mass of the cylinder and liquid, and subtract the mass of the cylinder from it to get solely the mass of the liquid. Calculate density

Question 6

How an the percentage error be reduced for the measurement of the density of a liquid

Answer 6

Pour as much water as possible into the measuring cylinder r

Question 7

How is the density of an irregular solid calculated?

Answer 7

Measure the mass of the object using a top pan balance, immerse the object on a thread into liquid in a measuring cylinder and measure the displacement of water to get the volume of the object. Calculate the density

Question 8

Alloy definition

Answer 8

A solid mixture of two or more metals

Question 9

How is the density of an alloy calculated?

Answer 9

There are two metals A and B for an alloy of Volume V. To get the mass of metal A, multiply its density A by its volume A. To get mass of metal B, multiply its density by its volume. To get total density, use the sum of the mass of metal A and B and divide by the total given volume

Question 10

What is Hooke’s Law?

Answer 10

The force need to stretch a spring is directly proportional to the extension of the spring from its natural length

Question 11

What does k refer to in hooke’s law

Answer 11

Spring constant

Question 12

What is the unit for k

Answer 12

N/m

Question 13

What happens to a spring that is stretched beyond its elastic limit

Answer 13

It does not return to its original length when the force is removed from it

Question 14

Springs in parallel
When a weight is supported by two springs parallel to each other, what is the extension of each spring?

Answer 14

The extension is the same

Question 15

For springs in parallel what is the effective spring constant

Answer 15

k=k(1)+k(2)

Question 16

For springs in parallel how is the weight calculated?

Answer 16

force of spring 1 + force of spring 2
Or spring constant of the sum of both springs x extension

Question 17

Springs in series: what is the tension in each spring equal to?

Answer 17

Weight acting on the spring

Question 18

Springs in series: how is the extension of spring A found?

Answer 18

Weight/spring constant of A

Question 19

Springs in series: what is the total extension for springs in series?

Answer 19

extension of spring A + extension of Spring B

Question 20

Springs in series: what is the equation that gives the effective spring constant of two springs in series?

Answer 20

1/k = (1/k1)+(1/k2)

Question 21

What does the energy stored in a spring look like on a force extension graph?

Answer 21

It is the area under the graph

Question 22

How is the area under a graph related to the energy stored in a stretched spring?

Answer 22

The work done to stretch a spring from its up stretched length = 1/2 x F x e
F=ke
Area = 1/2 x ke x e = 1/2 ke^2

Question 23

What is the definition of elasticity of a solid material

Answer 23

The materials ability to regain its shape after it has been deformed or distorted and the forced that deformed it have been released

Question 24

What is deformation that stretched an object called?

Answer 24

Tensile

Question 25

What is deformation that compresses an object called?

Answer 25

Compressive

Question 26

What is the tensile stress for a wire of length L and area of cross section A under tension? What is the unit

Answer 26

Force of Tension/area of cross section Pascal (N/m^2)

Question 27

What is the tensile strain for a wire of length L and are of cross section A under tension? Units?

Answer 27

extension/original length No unit as strain is a ratio

Question 28

What is the definition of toughness?

Answer 28

The measure of energy needed to break a material

Question 29

What is the definition of stress?

Answer 29

The tension per unit cross sectional area

Question 30

What is the definition of strain

Answer 30

The extension per unit length

Question 31

What is Young’s modulus?

Answer 31

The value of stress/strain

Question 32

What is the equation for Young’s modulus?

Answer 32

(Tensile force x original length)/(area of cross section x extension)

Question 33

For an stress-strain graph, what is the point E representing?

Answer 33

The point E represents the elastic limit which is the point beyond which the wire is permanently stretched and suffers plastic deformation

Question 34

What is the yield point on the stress strain graph?

Answer 34

The point beyond the elastic limit where the wire weakens temporarily

Question 35

After yield point 2, what does a small increase in tensile stress result in in regard to strain?

Answer 35

A large increase in tensile strain as the material of the wire undergoes plastic flow

Question 36

What is ultimate tensile stress?

Answer 36

Where the wire loses its strength, extends and becomes narrower at its weakest point (necking)

Question 37

How can the stiffness of different materials be compared?

Answer 37

Using the gradient of the stress strain line of each material - equal to the Young’s modulus of the materials.

Question 38

What is the strength of a material?

Answer 38

The materials ultimate tensile stress, which is its maximum tensile stress

Question 39

What is the difference between a brittle and ductile material on a stress strain graph?

Answer 39

A brittle material snaps without any noticeable yield point, a ductile material can be drawn into a wire and is deformed significantly before breaking

Question 40

For a metal wire: what does the unloading curve look like for a wire that has not exceeded its elastic limit?

Answer 40

The unloading curve is the same as the loading curve

Question 41

For a metal wire: when the elastic limit has been exceeded, what does the unloading curve look like?

Answer 41

The unloading curve is parallel to the loading line however the wire has plastically deformed and has a permanent extension - doesn’t return to original length

Question 42

For a rubber band: describe and explain the unloading curve look like compared to the loading curve?

Answer 42

The change in length is greater during unloading however it returns to the original length. The unloading curve is below the loading curve. The rubber band remains elastic

Question 43

Does a rubber band have a low or high limit of proportionality

Answer 43

Low

Question 44

For a polythene strip: describe and explain the unloading curve

Answer 44

The unloading curve does not return to the original length but the extension during unloading is greater than during loading. The polythene strip is plastically deformed

Question 45

Does a polythene strip have a high or low limit of proportionality

Answer 45

Low

Question 46

What is the work done/elastic energy to stretch a metal wire provided the limit of proportionality is not exceeded?

Answer 46

1/2 (Tensile force x extension)

Question 47

What does the area between the loading and unloading curve of rubber represent?

Answer 47

The difference between the energy stores by the rubber and the useful energy recovered from it

Question 48

What does the area between the loading and unloading curves of a polythene strip represent?

Answer 48

As it doesn’t return to original length it represents the internal energy of molecules and the work done to plastically deform the strip