...
The
...
basic
...
units
...
for
...
all
...
Software
...
include
...
force
...
(lbs,
...
kip,
...
N,
...
kN,
...
etc.),
...
length
...
(ft,
...
in,
...
m,
...
mm,
...
etc.),
...
time
...
(second),
...
and
...
temperature
...
(F,
...
C).
...
...
is
...
then
...
derived
...
from
...
these
...
values.
...
Some notes which concern force and mass units are as follows:
- lbs and kips are only used as force units, not mass units
- Consistent mass units are force divided by unit acceleration, given as F/(L/T
...
- 2),
...
- in
...
- which
...
- L
...
- is
...
- length
...
- and
...
- T
...
- is
...
- time.
...
- Weight
...
- is
...
- a
...
- force.
...
- Given SI units,
...
- in
...
- which
...
- force
...
- is
...
- in
...
- Newtons
...
- (N),
...
- the
...
- consistent
...
- mass
...
- unit
...
- is
...
- N*sec
...
- 2/m
...
- =
...
- kg.
...
- Given US Customary,
...
- in
...
- which
...
- force
...
- is
...
- in
...
- pounds
...
- (lbs),
...
- the
...
- consistent
...
- mass
...
- unit
...
- is
...
- lbs*sec
...
- 2/ft
...
- =
...
- slug.
...
- Under
...
- a
...
- unit
...
- acceleration,
...
- a
...
- mass
...
- of
...
- one
...
- slug
...
- generates
...
- a
...
- one
...
- pound
...
- force.
...
- When
...
- accelerated
...
- by
...
- gravity
...
- (g),
...
- this
...
- same
...
- mass
...
- generates
...
- a
...
- force
...
- of
...
- 32.2
...
- lbs.
...
- The
...
- pound-mass
...
- unit
...
- is
...
- not
...
- a
...
- consistent
...
- unit,
...
- where
...
- 1
...
- slug
...
- =
...
- 32.2
...
- pound-mass.
...
- Additional
...
- information
...
- is
...
- available
...
- in
...
- the
...
- Wikipedia
...
- article.
- Weight density has units of F/L3
- Consistent mass density has units of (F/(L/T
...
- 2))/L
...
- 3 =
...
- F*T
...
- 2/L
...
- 4
- The relationship between weight and mass, and weight density and mass density, is W = M * g, all in consistent units.
- To convert weight density W = 150 lbs/ft3 into mass density (kip-in),
...
- the
...
- calculation
...
- proceeds
...
- as
...
- follows:
...
M = W / g = 150 lbs/ft3 / (32.2
...
- ft/sec
...
- 2)
...
- =
...
- 4.658
...
- lbs*sec
...
- 2/ft
...
- 4 * (kip
...
- /
...
- 1000
...
- lbs)
...
- *
...
- (ft
...
- /
...
- 12
...
- in)
...
- 4 =
...
- 2.246E-7
...
- kip*sec
...
- 2/in4