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Units Flashcards

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1
Q

nutritionist’s calories

A

Cal or kcal = 1000 cal

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2
Q

1 cal = ? J

A

4.18 J

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3
Q

The mass balance states

A

input = output

X + Y = 100

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4
Q

Standardization

A

the process where the fat content of milk products is adjusted by the addition of cream or skim-milk.

input-output = accumulation

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5
Q

steady state is achieved when

A

there is no accumulation of material, i.e. input = output

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6
Q

batch operations, normally runs on

A

runs on a time basis (hourly)

100 = m+C

[m = mass of water removed; C = mass of concentrate produced]

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7
Q

If 100 kg h-‘ of liquid containing 12% total solids is to be concentrated to produce a liquid containing 32% total solids, how much water is removed each hour?

A

100 = m+C

100 x 0.12= C x 0.32

It is assumed that the water leaving the evaporator contains no solid. Thus, C = 37.5kg , m = 62.5kg

Water needs to be removed at the rate of 62.5 kg h^-1

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8
Q

accumulation

A

input +production-output = accumulation

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9
Q

kgm^-3 is equivalent to

A

g l ^-1

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10
Q

In a spontaneous change, heat (energy) is always transferred from _______ to ___________, until ___________ is achieved

A

from an object at a high temperature to one at a lower temperature
until thermal equilibrium is achieved

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11
Q
  • C = ? *F

* F = ? *C

A
  • C = (*F- 32) x (5/9)

* F= (9/5) x *C +32

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12
Q

absolute zero = 0 K

A

all molecular motion stops and the kinetic energy of the molecule becomes zero.

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13
Q

K = ? *C

A
  1. 15 + *C
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14
Q

Carnot efficiency (CE)

A

a measure of the conversion of heat to work

CE = [(Heat 1 - Heat 2) / Heat 1] x 100

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15
Q

Electric current (A)

A

a measure of the flow of electrons

unit = ampere (A)

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16
Q

One ampere (1 A) is

A

flow of electrons which, when flowing down two long parallel conductors, of negligible cross-sectional area, placed 1 metre apart in a vacuum produces between the two wires a force of 2x 10^-7 N per metre of the length

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17
Q

Luminous intensity unit

A

candela (cd)

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18
Q

units of velocity

A

m s^-1

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19
Q

surface area of a circle

A

r x r x pi

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20
Q

surface area of a sphere

A

4 x pi x r x r = pi x Dx D

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21
Q

1 m^2 = ? cm^2 = ? ft ^2

A

10^4 cm^2 = 10.76 ft ^2

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22
Q

volumetric flow rate (Q)

units

A

Volume of fluid that passes through a given volume of space per unit of time

m^3 s^-1

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23
Q

volume of a sphere

A

(4/3) x pi x r^3

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24
Q

surface-area-to-volume ratio

A

[2 (r + h) ] / rh

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25
Q

When heating an object, maximize the surface-area-to-volume ratio will

A

maximize the heat transfer rate and reduce the time required

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26
Q

volume unit

A

m^3

27
Q

Density

A

mass/ volume kg m^-3

28
Q

Specific gravity

A

the mass of a substance divided by the mass of an
equal volume of water

has no units

29
Q

velocity

A

as distance covered divided by time taken to cover that distance.

m s^-1

30
Q

average velocity (v)

A

volumetric flow rate Q (m^3 s^-1) / cross-sectional area A (m^2)

m s^-1

31
Q

average velocity for a pipe or tube with diameter D

A

v = Q / pi x r^2

32
Q

Momentum units

A

kg m s^-1

33
Q

angular velocity

A

the velocity of an object moves in a circle of radius r
angle subtended per unit time : (w) or (N)

(w) rad s^-1 (N) rev s^-1
(w) = 2 pi N

34
Q

1 rad = ? *

1 rev = ? rad

A

2 pi rad = 1 rev = 360*

1 rad = 57.3*

35
Q

acceleration

A

the rate of change in velocity

m s^-2

36
Q

terminal velocity

A

An object moving with a constant velocity has no acceleration

37
Q

gravity

A

9.81 m s^-2.

38
Q

Force

units

A

masses, electric charges, magnetic poles, nuclear particles

kg m s^-2 or N

39
Q

rheology

A

study of the deformation of objects under the influence of applied forces

40
Q

Newton’s second law of motion

A

when an object changes momentum, it is subjected to a force Fand that the magnitude of the force is proportional to the rate of change in momentum.

force = rate of change in momentum

41
Q

centrifugal force

A

an outward force acting on the object, to balance the centripetal force and keep the object in the same relative position when moving round a circle a constant tip speed

m r w^2 = [m v^2] / r

42
Q

centripetal force

A

an inward force apply to an object when it is moving round a circle at a constant tip speed.
It is constantly changing its velocity because of its change in direction.

centripetal force (N) = mass (kg) x centripetal acceleration (m s^-2) = m v^2 / r

43
Q

centripetal acceleration

A

centripetal acceleration (m s^-2) = v^2 / r or r w^2

v = velocity (m/s) 
r = circular radius (m)
44
Q

Newton’s third law

A

for every acting force there is an equal and opposite reaction force

45
Q

pressure

A

force / applied surface area

kg m^-1 s^-2 or N m^-2 or Pa

46
Q

units of fluid density

A

kg m^-3

47
Q

absolute pressure

A

p = p g h

p = fluid density  (kg m^-3)
g = gravity (m s^-2)
h = height of fluid head (m)

absolute pressure = gauges pressures + atmospheric pressure

48
Q

Positive pressure

A

gauges pressures > atmospheric pressure

49
Q

Vacuum pressure

A

gauges pressures < atmospheric pressure

50
Q

Shear stress.

A

The effect of a force acting parallel to a given area.

51
Q

Frequency:

A

v = n/t = s^-1 or Hz

52
Q

Period

A

T = t/n = 1 / v = 2pi/ w (s)

53
Q

Different velocity

A
  • Force acts same line velocity
  • Force acts perpendicular to velocity
  • Force acts towards “o” and perpendicular to velocity
  • Forces is variable proportional to its distance to “o”
54
Q

Surface area of a cylinder

A

pi D L + 2 x pi r^2

55
Q

Work

A

a moving force through distance. It’s energy

kg m^-2 s or J

56
Q

Power

A

the rate of doing work.
= work done/ time

Watt = joule / second [ W or J s^-1]

57
Q

thermal conductivity

A

J s ^-1 m^-1 K^-1 or W m^-1 K^-1

58
Q

electricity bills unit

A

k W h

59
Q

pumping power

A

(pi - po) /pg

pi = inlet pressure 
po = outlet pressure 
p = fluid density  (kg m^-3)
g = gravity (m s^-2)
60
Q

theoretical power Po (W) delivered to the fluid

A

Po (W) = mass flow rate (kg s^-1) X head developed (m) x

acceleration due to gravity (m s^-2)

61
Q

molarity of solution

A

concentration / molecular weight

62
Q

concentration

A

mass of solid / total volume

or weight/ weight

63
Q

no of moles

A

mass / molecular weight

physics (6 decks)

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