materials

Question 1

density

Answer 1

p=m/v, mass per unit volume

Question 2

upthrust

Answer 2

the weight of fluid displaced

Question 3

why do objects submerged in a fluid experience upthrust

Answer 3

the fluid which is displaced wants to take up the volume. if it is floating, weight=upthrust.

Question 4

stokes law

Answer 4

F=6rvnπ, used to calculate viscous drag

Question 4

viscous drag

Answer 4

the resistive force experienced by an object moving in fluid

Question 5

conditions for stokes law

Answer 5

-object is small and spherical
-object moves at low speed with laminar flow

Question 6

laminar flow

Answer 6

the particles in a fluid move by following smooth paths with little to no mixing between adjacent layers of the fluid

Question 7

turbulent flow

Answer 7

the particles in the fluid mix between layers and form separate currents. often described as chaotic

Question 8

viscosity

Answer 8

measure of how resistant a fluid is to deformation. determined by the internal friction forces that occur between adjacent layers of the fluid. viscosity is temperature dependent

Question 9

hookes law

Answer 9

extension is directly proportional to the force applied, given that environmental conditions are kept constant
∆F=k∆x

Question 10

Youngs modulus

Answer 10

value which describes the stiffness of a material
YM=stress/strain

Question 11

strain

Answer 11

caused by stress, change in length over the original length
strain=∆x/x

Question 12

force extension graph

Answer 12

shows how extension varies with force, hookes law can be demonstrated by a straight Lin through the origin, directly proportional.

Question 12

stress

Answer 12

force applied per unit cross-sectional area
stress=F/A

Question 13

what is point p on a force extension graph

Answer 13

limit of proportionality, after this point hookes law is mot obeyed

Question 14

what is point e on a force extension graph

Answer 14

elastic limit, after this point the material will not return to its original shape and undergo plastic deformation

Question 15

what is point y on a force extension graph

Answer 15

yield point, where extension starts to increase with no increase in load

Question 16

how is energy lost in plastic deformation

Answer 16

work is done to move atoms apart, so energy is dissipated as heat

Question 17

stress-strain graphs

Answer 17

describe the behaviour of a material

Question 18

ductile

Answer 18

can undergo large amounts of plastic deformation before fracturing

Question 19

brittle

Answer 19

material undergo little to no plastic deformation before fracturing

Question 20

plastic

Answer 20

experiences a large amount of extension as load is increased

Question 21

breaking stress

Answer 21

value of stress at which the material will break apart, this value will depend on the conditions of the material eg. its temperature

Question 22

elastic strain energy

Answer 22

when work is done on a material to stretch or compress it, this energy is stored as elastic strain energy, it can be found by finding the area under a force extension graph or using the formula ∆E=0.5F∆x

Question 23

spring in ‘series’

Answer 23

extension is doubled

Question 24

springs in ‘parallel’

Answer 24

extension is halved