ch 7 - matter and materials

Question 1

density definition

Answer 1

mass per unit volume

. symbol = /p/ (rho)
. units = kg m¯³, g cm¯³

Question 2

density formula

Answer 2

p = m/v

Question 3

1000 kg m-3 =

Answer 3

1 g cm-3

Question 4

density of water ≈

Answer 4

1000 kg m-3

Question 5

what is pressure

Answer 5

the normal/perpendicular force acting per unit cross sectional area

Question 6

what is pressure

Answer 6

the normal/perpendicular force acting per unit cross sectional area

. symbol = p
. units = Pa = Nm-2

Question 7

pressure formula (solid)

Answer 7

p = F/ A

Question 8

pressure formula (fluid)

Answer 8

<>p = pgh
p = <>p + P atm

Question 9

change in pressure in fluids formula derivation

Answer 9

vol = Ah
mass of water = p * Ah
weight of water = pAhg
change in pressure = F/A
change in pressure = pAh*g/A
change in pressure = pgh

Question 10

what is Archimedes’ principle

Answer 10

the upthrust on a body is equal to the weight of the fluid that displaces it

Question 11

upthrust formula

Answer 11

phV

Question 12

upthrust formula derivation

Answer 12

= F2 - F1
= pg(h2 - h1) A
= pghA
= pgV

Question 13

compressive forces

Answer 13

describes a force that squeezes and shortens an object

Question 14

what are tensile forces

Answer 14

associates with tension or pulling

Question 15

what is extension

Answer 15

the increase in the length of a material from its original length

Question 16

hooke’s law

Answer 16

force is proportional to extension until the limit of proportionality/ elastic limits

Question 17

spring constant

Answer 17

the force per unit extension for a spring, unit = Nm-1

k = F/x

Question 18

the limit of proportionality

Answer 18

the point beyond which extension is no longer proportional to the force

Question 19

what is elastic deformation

Answer 19

an object that returns ti its initial length when the force is removed has deformed elastically

Question 20

what is platic deformation

Answer 20

an object that does not return to its initial length when the force is removed is deformed permanently

Question 21

what is an elastic limit

Answer 21

the value of stress beyond which an object will not return to its original dimentions

Question 22

what is strain

Answer 22

extension / length

symbol : curved E
unit : none

Question 23

what is stress?

Answer 23

force per unit cross sectional area that acts at right angles to a surface

F/A

unit : Pa
symbol : sigma

Question 24

what is Young modulus?

Answer 24

the stress in material divided by the strain

E = stress / strain
gradient

high young modulus, high stiffness

Question 25

what is elastic potential energy / strain energy

Answer 25

energy stored in a body due to a chnage in its shape

Question 26

elastic potential energy formula derivation

Answer 26

work done
final force/2 * extension
0.5Fx

OR

area = 0.5 bh
0.5Fx

Question 27

elastic potential energy formula

Answer 27

E = 0.5Fx = 0.5 kx²

Question 28

area under a force extension graph

Answer 28

work done by force