Mechanical Engineering Principles

A LIST OF FORMULAE 281

Formula Formula symbols Units

compound pendulum T= 2 π

√

(kG^2 +h^2 )

gh

s

Force ratio =

load

effort

Movement ratio=

distance moved by effort

distance moved by load

Efficiency =

force ratio
movement ratio
Kelvin temperature=degrees Celsius+ 273

Quantity of heat energy
=mass×specific heat capacity×change in temperature

Q=mc(t 2 −t 1 )

New length = original length+expansion L 2 =L 1 [1+α(t 2 −t 1 )]m

New surface area=original surface area+increase in A 2 =A 1 [1+β(t 2 −t 1 )]m^2
area

New volume=original volume+increase in volume V 2 =V 1 [1+γ(t 2 −t 1 )]m^3

Pressure =

force

area

p=

F

A

Pa

=density×gravitational acceleration×height p=ρgh Pa

1bar= 105 Pa

Absolute pressure=gauge pressure

+atmospheric pressure

Metacentric height, GM GM=

Px

W

cotθ m

Bernoulli’s equation

P 1

ρ

+

v^21

2

+gz 1 =

P 2

ρ

+

v^22

2

+g(z 2 +hf)

Coefficient of discharge Cd=Cv×Cc

Characteristic gas equation

p 1 V 1

T 1

=

p 2 V 2

T 2

=k

pV=mRT

Circular segment

In Figure F1, shaded area=

R^2

2

(α−sinα) a

R

Figure F1