MECHANICAL_ENGINEERS_MANUAL

MECHANICAL ENGINEER’S MANUAL


By : ENGR. YURI G. MELLIZA




1

,DEFINITION OF TERMS

Mass: It is the absolute quantity of matter in it.
m – mass, kg

Conversion
1 kg = 2.205 lbs
1 Metric Ton = 1,000 kg
1 Ton = 2000 Lbs

Velocity: It is the distance per unit time.
d m
v
t sec
Where
d – distance, m
t – time, sec

Conversion
1 meter = 3.28 ft = 100 cm = 1000 mm
1 ft. = 12 inches

Acceleration: Rate of change of velocity with respect to time.
dv m
a
dt sec 2

Gravitational Acceleration: It is the acceleration due to gravity.

At standard condition or Sea level condition:
g = 9.81 m/sec2 = 32.2 ft/sec2

Force: It is the mass multiplied by the acceleration.


F  ma N (Newton)
ma
F KN (Kilo Newton)
1000

Newton: It is the force required to accelerate 1 kg mass at the rate of 1 m/sec per second.

Where:
m – mass in kg
a – acceleration in m/sec2

Weight: It is the forge due to gravity.

W  mg N
mg
W KN
1000
where
m
g - gravitatio nal accelerati on,
sec2
 Standard gravitatio nal accelerati on 
m
g  9.81
sec2




2

,Force of Attraction: From Newton’s Law of Gravitation the force of attraction between two masses m 1 and m2 is given by the
equation:

Gm1m 2
Fg  Newton
r2
Where:
m1 and m2 - masses in kg
r - distance apart in meters
G - Gravitational constant in N-m2/kg2
N - m2
G  6.670 x 10-11
kg 2


PROPERTIES OF FLUIDS

Density () - it is the mass per unit volume.
m kg
ρ
V m3

Where:
m - mass, kg
V - volume , m3
Conversion:
lb kg
1  16.0185
ft 3 m3
kg lb
1 3
 62,427.9606
cm ft 3
g kg
1 1 3
liter m

Specific volume () - it is the volume per unit mass or the reciprocal of its density.

V m3
υ
m kg
1 m3
υ
ρ kg

Specific weight () - it is the weight per unit volume.
W KN
γ
V m3
mg KN
γ
1000V m 3
ρg KN
γ
1000 m 3
1000γ kg
ρ
g m3

Specific Gravity Or Relative Density (S):

FOR LIQUIDS: Its specific gravity or relative density is equal to the ratio of its density to that of water at standard temperature and
pressure.

ρ γ
SL   L
ρw γw




3

, At standard condition:
water = 1000 kg/m3
water = 9.81 KN/m3

FOR GASES: Its specific gravity or relative density is equal to the ratio of its density to that of either air or hydrogen at some
specified temperature and pressure
PV  mRT
P kg
ρ
RT m 3
8.3143 KJ
R
M kg - K




Where:
ah - density of either air or hydrogen at some value of P and T.



Equation of State for Gases

Conversion
F  32
C 
1 .8
F  1.8(C)  32
Where:
P – absolute pressure in KPa
V – volume in m3
m – mass in kg
R – Gas constant in KJ/kg-K
T – absolute temperature in K.
M – molecular weight of gas, kg/kgmol




Temperature: It is the measure of the intensity of heat.

FAHRENHEIT SCALE
ρG
SG 
Freezing Point = 32F
Boiling Point = 212F
CENTIGRADE SCALE ρ AH
Freezing Point = 0C
Boiling Point = 100C
ABSOLUTE SCALE
R = F + 460
K = C + 273




4