Chapter 6: materials

Question 1

define tensile force

Answer 1

force that produces an extension

Question 2

define compressive force

Answer 2

force that produces a compression

Question 3

define elastic limit

Answer 3

the point after which an object becomes permanently deformed

Question 4

define elastic

Answer 4

material that allows the object to return to its original shape and size after a force has acted on it

Question 5

define plastic

Answer 5

material that causes an object to become permanently deformed after a force has acted on it

Question 6

what is the force/spring constant equation

Answer 6

F = k e/x
Force = spring constant x extension

Question 7

what is the equation for working out the spring constant for springs in parallel

Answer 7

K1 + K2 + K.. = Kt

spring constant 1 + spring constant 2 + etc = total spring constant

Question 8

what is the equation for working out the spring constant for springs in series

Answer 8

1/K1 + 1/K2 + etc = 1/Kt

1/spring constant 1 + 1/spring constant 2 + etc = 1/total spring constant

Question 9

describe what the force/extension graph would look like for a strong object

Answer 9

a strong object would have a steep gradient then a curve then it would stop

Question 10

describe what the force/extension graph would look like for a polymer

Answer 10

a polymer has a curve that looks like a cubic graph before snapping or having a linear return whilst being permanently deformed

Question 11

what happens the closer you get to the elastic limit

Answer 11

it becomes harder to stretch an object

Question 12

what is the elastic potential energy equation

Answer 12

EPE = 0.5 k e^2

elastic potential energy = 0.5 x spring constant x extension squared

Question 13

what is the gravitational energy equation

Answer 13

GPE = m g h

Gravitational potential energy = mass x gravitational field strength x height

Question 14

what is stress

Answer 14

measure of force compared to the area acted upon

Question 15

what is the stress equation

Answer 15

σ = F/A
stress = force/area

Question 16

what are the units for stress

Answer 16

Pa Pascals

Nm^-2 Newtons per metre squared

Question 17

what quantity is stress

Answer 17

vector because it has direction and magnitude

Question 18

what is strain

Answer 18

strain is a ratio that is a measure of extent of deformation

Question 19

what is the linear strain equation

Answer 19

Ɛ = x/L or e/L

linear strain = extension/length

Question 20

what are the three forms of strain and what do they mean

Answer 20

elastic (object returns to original shape and size)
plastic/ductile (object is permanently deformed)
brittle (object will snap)

Question 21

what is Young’s Modulus

Answer 21

measure of the stiffness of an object

Question 22

what is the Young’s Modulus equation

Answer 22

E = σ/Ɛ

Youngs Modulus = stress/strain