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Unit 5 BTEC science > physics > Flashcards

physics Flashcards

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1
Q

what is power

A

the rate of doing work

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2
Q

what is the formula for power

A

power= workdone/time

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3
Q

what are the units for power

A

watts

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4
Q

what are the units for work done

A

joules

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5
Q

what are the units for time

A

seconds

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6
Q

what is efficiency

A

the ratio of two energies, it has no units

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7
Q

what is the formula for efficiency

A

efficiency= useful energy (power) output/ total energy (power) input

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8
Q

what is the second law of thermodynamics

A

-energy from a heat source= useful work done + energy given to a cold sink
-Q1= W+Q2
W=Q1-Q2

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9
Q

what is the formula for the second law of thermodynamics

A

efficiency= 1 (big 1) -Q out/Q in

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10
Q

what is T1

A

temperature in (temp of the source)

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11
Q

what is Q1

A

total energy in from source

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12
Q

what is W

A

useful energy out for work done

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13
Q

what is T2

A

temperature out (temp of the sink)

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14
Q

what is Q2

A

waste product/gives out energy in the cold sink

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15
Q

what is the max theoretical efficiency

A

Q1/Q2 = T1/T2

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16
Q

what is COP

A

Coefficient Of Perfomance, it is the ratio of heat supplied to the high-temperature reservoir to work done.

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17
Q

what is the formula for COP

A

1 (BIG ONE) - Q2/Q1

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18
Q

what is the ideal gas

A

the temperature of a gas is directly proportional to the average kinetic energy of the molecules of the gas.

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19
Q

what is the formula for pressure

A

pressure= force/ area

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20
Q

what is the formula for kinetic energy

A

1/2 X mass X velocity squared

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21
Q

what is the formula for ideal gas

A

PV=NKT

pressure X volume= number of molecules in the gas X boltzmann constant X temperature

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22
Q

what is the Boltzmann’s constant

A

1.38x10-3

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23
Q

what is specific heat capacity

A

the energy needed to raise the temperature of 1kg of a substance by 1c

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24
Q

what does the temperature depend on if a substance is heated

A
  • the mass of the substance
  • what material the substance is made from
  • the amount of energy supplied
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25
Q

what is the formula for specific heat capacity

A

delta E= M x C x delta

change in energy = mass X specific heat capacity X change in temp

26
Q

what are the assumptions about ideal gas

A
  • particles are in continuous random motion
  • the volume of particles is very small compared to the volume of the gas
  • particles are along way from eachother and dont interact except when they collide.
  • collisions are elastic (no kinetic energy is lost during collisions)
27
Q

what is an isothermal change and when does it take place

A
  • it takes place at a constant temperature
  • thermal energy can be added or released in order to keep the temperature constant
  • when 2 bodies reach thermal equilibrium
28
Q

when can a gas only be changed isothermally

A
  • it is in a good conducting, thin-walled container
  • it is surrounded by a constant temperature reservoir
  • the change occurs very slowly
29
Q

what is specific latent heat

A

the amount of energy needed to change the state of mass of a pure substance without changing the temperature

30
Q

what is the equation for specific latent heat

A

Q=MxL

thermal energy= mass X specific latent heat

31
Q

what is plastic deformation

A

when a shape/size changes and becomes permanent

32
Q

what is hookes law

A

the extension of a spring is directly proportional to the force applied to it

33
Q

what is the for hookes law

A

F=K x delta X

34
Q

what is elastic strain energy

A

-when a spring is stretched potential energy is stored

35
Q

what is the formula for elastic strain energy

A

energy= 1/2 X force X extension

36
Q

what is tensile force

A

when a spring is stretched and made long, the spring gets deformed

37
Q

what is stress

A

when a load is attached on a spring and it feels a pressure, the pressure is called stress

38
Q

what is strain

A

when a load is attached on a spring the length increases, the extension of the spring is called strain

39
Q

what is the formula for stress

A

force/ corss section area

40
Q

what is the formula for strain

A

extension/ orgional length

41
Q

what is breaking stress

A

the stress required to break the shape

42
Q

what is young modulus

A

a measure of the stiffness of a material

43
Q

what is the formula for young modulus

A

stress/ strain

44
Q

what are Newtonian fluids

A
  • the viscosity of the fluid doesn’t change with the rate of flow
  • fluids are either gases or liquids
45
Q

what is a adiabatic process

A

-no heat transfer so work input= internal energy gained

46
Q

what is the kinetic theory of matter

A
  • solids have a fixed position and but are able to vibrate
  • liquids flow past each other and collide while still vibrating
  • gases travel fast between collisions, atoms still vibrate and molecules can spin
47
Q

what is absolute zero

A

where all thermal energy has been removed

all molecules are in the lowest possible energy state

48
Q

what is the formula for the first law of thermodynamics

A

Q= delta U + W

heat in = energy change in the system + work out

49
Q

what is the elastic limit

A

-highest tensile stress with full elastic recovery

50
Q

what is ductility

A

the ability to be shaped by plastic flow under tension eg drawing into rods, wires or tubes

51
Q

what is malleability

A

the ability to be shaped by plastic flow under compression eg rolling or hammering into sheets

52
Q

what is ultimate tensile strength

A

the highest stress a material can sustain just before it breaks

53
Q

what is creep

A

a slow version of plastic deformation, it increases with temperature

54
Q

what is fatigue

A

caused by repeated cycles of loading and unloading which causes a crack

55
Q

when does laminar/streamline flow occur

A
  • occurs at lower values of flow rate and pressure difference
  • drift of particles are all parallel and in the same sense
  • velocity changes across the flow of the stream
  • energy efficient
56
Q

when does turbulent flow occur

A
  • occurs at higher flow rates
  • absorbs more energy as it generates more resistance to flow
  • its chaotic
57
Q

what is viscosity

A

resistance to flow

58
Q

what is a Newtonian fluid

A

a fluid that has a constant viscosity

59
Q

what is a non-Newtonian fluid

A

a fluid that changes its viscosity

  • they change viscosity as soon as there is a shear stress
  • brushing, sliding or stirring a liquid provides shear stress
60
Q

what are examples of non-newtonian fluid

A 
shear thinning (pseudoplastic) 
shear thickening (dilatant) fluids
61
Q

what are Bingham plastics

A

behave like solids at low shear stresses, but above a yield stress they begin to flow

62
Q

what are examples of bingham plastics

A

toothpaste, mud, mayonnaise

Unit 5 BTEC science (3 decks)

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