Materials

Question 1

What is deformation?

Answer 1

When a force changes the shape and size of a body

Question 2

What is tensile deformation?

Answer 2

When 2 forces stretch a body

Question 3

What is compressive deformation?

Answer 3

When 2 forces compress a body

Question 4

What happens to a spring when tensile forces are applied?

Answer 4

It will extend

Question 5

What happens to a spring when compressive forces are applied?

Answer 5

It will compress

Question 6

What is Hookes Law?

Answer 6

The extension of the material is directly proportional to the applied force up to the limit of proportionality

Question 7

What is Hookes law equation?

Answer 7

F = kx

F = force N
k = force constant Nm^-1
x = extension m

Question 8

What is the force/spring constant a measure of?

Answer 8

Stiffness of the material

Question 9

The larger the spring constant, the ________ the material

Answer 9

Stiffer

Question 10

What is a brittle material?

Answer 10

A material that fractures after its elastic limit is exceeded

Question 11

What is a ductile material?

Answer 11

A material that has the capacity to deform plastically, such as being drawn into wire

Question 12

What is the limit of proportionality?

Answer 12

The point beyond which Hookes law is no longer applicable/ true when stretching a material

Question 13

What is the elastic limit?

Answer 13

The maximum amount a material can be stretched and still return to its original length - it is always after the limit of proportionality

Question 14

What does a general force-extension graph look like?

Answer 14

Question 15

What does a force-extension graph look like for a metal wire?

Answer 15

Question 16

What does a force-extension graph look like for rubber?

Answer 16

Question 17

What does a force-extension graph look like for polyethene?

Answer 17

Question 18

How do you investigate force-extension characteristics?

Answer 18

Question 19

What is the area under a force-extension graph equal to?

Answer 19

The work done - this is true whether the material obeys Hookes law or not

Question 20

What is elastic potential energy?

Answer 20

The energy stored within a material when it is stretched or compressed

Question 21

What are the equations for elastic potential energy?

Answer 21

E = 1/2 Fx
E = 1/2 kx^2

E = elastic potential energy
F = force N
x = extension m
k = force constant

Question 22

What is tensile stress?

Answer 22

The force extended per unit cross-sectional area

Question 23

What is tensile strain?

Answer 23

The extension per unit length of a material

Question 24

What is the equation for tensile stress?

Answer 24

σ = F / a

σ = stress pa
F = force N
A = area m^2

Question 25

What is the equation for tensile strain?

Answer 25

ε= x / L

ε= strain (no units)
x = extension (m)
L = length (m)

Question 26

What is ultimate tensile strength?

Answer 26

The maximum of load/ stress a material can handle until it fractures and breaks

Question 27

What is the equation for Young Modulus?

Answer 27

E = σ/ ε = FL/ Ax

Question 28

How do you investigate Young Modulus?

Answer 28

Question 29

What are the features of a stress-strain graph?

Answer 29

Question 30

What does a stress-strain graph look like for a brittle material?

Answer 30

Question 31

What does a stress-strain graph look like for a ductile material?

Answer 31

Question 32

What does a stress-strain graph look like for a polymeric material?

Answer 32

Question 33

What is elastic deformation?

Answer 33

When the load is removed, the object will return to its original shape

Question 34

What is plastic deformation?

Answer 34

When the load is removed, the object will not return to its original shape or length - the material is permanently deformed