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Unit 5 BTEC science > physics > Flashcards

physics Flashcards

(62 cards)

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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
what is the formula for specific heat capacity
delta E= M x C x delta | change in energy = mass X specific heat capacity X change in temp
26
what are the assumptions about ideal gas
- 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
what is an isothermal change and when does it take place
- 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
when can a gas only be changed isothermally
- it is in a good conducting, thin-walled container - it is surrounded by a constant temperature reservoir - the change occurs very slowly
29
what is specific latent heat
the amount of energy needed to change the state of mass of a pure substance without changing the temperature
30
what is the equation for specific latent heat
Q=MxL | thermal energy= mass X specific latent heat
31
what is plastic deformation
when a shape/size changes and becomes permanent
32
what is hookes law
the extension of a spring is directly proportional to the force applied to it
33
what is the for hookes law
F=K x delta X
34
what is elastic strain energy
-when a spring is stretched potential energy is stored
35
what is the formula for elastic strain energy
energy= 1/2 X force X extension
36
what is tensile force
when a spring is stretched and made long, the spring gets deformed
37
what is stress
when a load is attached on a spring and it feels a pressure, the pressure is called stress
38
what is strain
when a load is attached on a spring the length increases, the extension of the spring is called strain
39
what is the formula for stress
force/ corss section area
40
what is the formula for strain
extension/ orgional length
41
what is breaking stress
the stress required to break the shape
42
what is young modulus
a measure of the stiffness of a material
43
what is the formula for young modulus
stress/ strain
44
what are Newtonian fluids
- the viscosity of the fluid doesn't change with the rate of flow - fluids are either gases or liquids
45
what is a adiabatic process
-no heat transfer so work input= internal energy gained
46
what is the kinetic theory of matter
- 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
what is absolute zero
where all thermal energy has been removed | all molecules are in the lowest possible energy state
48
what is the formula for the first law of thermodynamics
Q= delta U + W | heat in = energy change in the system + work out
49
what is the elastic limit
-highest tensile stress with full elastic recovery
50
what is ductility
the ability to be shaped by plastic flow under tension eg drawing into rods, wires or tubes
51
what is malleability
the ability to be shaped by plastic flow under compression eg rolling or hammering into sheets
52
what is ultimate tensile strength
the highest stress a material can sustain just before it breaks
53
what is creep
a slow version of plastic deformation, it increases with temperature
54
what is fatigue
caused by repeated cycles of loading and unloading which causes a crack
55
when does laminar/streamline flow occur
- 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
when does turbulent flow occur
- occurs at higher flow rates - absorbs more energy as it generates more resistance to flow - its chaotic
57
what is viscosity
resistance to flow
58
what is a Newtonian fluid
a fluid that has a constant viscosity
59
what is a non-Newtonian fluid
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
what are examples of non-newtonian fluid
``` shear thinning (pseudoplastic) shear thickening (dilatant) fluids ```
61
what are Bingham plastics
behave like solids at low shear stresses, but above a yield stress they begin to flow
62
what are examples of bingham plastics
toothpaste, mud, mayonnaise

Unit 5 BTEC science (3 decks)

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