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7-5

ตารางที่ 7.2 ความสัมพนธระหวางระบบ USCS และ SI
ั
( Relationships Between USCS and SI Units for Selected Quantities )

Quantity USCS Units SI Units conversion

Name Symbol Name Symbol
Base Units

Length foot ft meter m :ft=0.3048 m.
inch in. 1 in.= 0.0254 m.

Mass pound lb kilogram kg. 1 lb=0.4536 kg.
kilopound kip 1 kip=163.6

kg.
time second sec second s 1 sec= 1s

temperature degree fahrenheit F degree Celsius C 1 F= 1.81 C+32
kelvin K t =t + 273.15
K C

Supp. Units
Plane angle degree adian ad = 0.0745rad.

Derived Units
2
2
2
2
Area square foot ft square meter m 1 ft =0.0929 m
3
3
3
2
Volume cubic foot ft cubic meter m 1 ft =0.0283 m
2
Velocity foot/second ft/sec meter/second m/s 2 1 ft/sec=0.3048
2
m/s
2
2
2
Acceleration (foot/second)/second ft/sec (meter/second)/secondft/sec 1ft/sec =0.3048
2
m/s
2
Force pound lb newton.,kg,m/sec N 1 lb=4.448 N
kilopound kip 1
kip=4448N
2
2
Pressure pound/foot psf pascal,N/m Pa 1 psf=47.88 Pa
2
pound/inch psi 1 psi=6895
Pa

Work, energy foot-pound ft-lb joule,N-m j 1 ft.lb=1.356 j
foot-kip ft-kip 1 ft-kip=1356 j

Frequency Cycle/sccond cps hertz, I/S Hz 1 cps= 1 Hz