A. 12. REFERENCES
537
Table A.7: Rules of Thumb
Acceleration of gravity « 9.81 m/s2
Density of freshwater « 1 000 kg/m3
Unit weight of freshwater ~ 9.80 kN/m3
Unit weight of saltwater ~ 10.05 kN/m3
3 000 psi concrete ~ 20 MPa concrete
Multiply
By
To Approximate
Error
meters
3
feet
9%
kilometers
0.6
miles
3%
square meters
10
square feet
7%
cubic meters
35
cubic feet
1%
cubic meters
1.3
cubic yards
1%
meters/second
3
feet/second
9%
kilometers/hour
0.6
miles/hour
3%
newtons
0.2
pounds
11%
kilopascals
0.15
pounds/inch2
3%
kilopascals
20
pounds/feet2
4%
kilonewtons/meter3
6
pounds/feet3
6%
A. 12 References
Petersen, M. S. 1980. “Recommendations for Use of SI Units in Hydraulics,” Journal of the Hydraulics Division, ASCE, Vol 106, No.
HY 12, pp. 1981-1993.
U.S. Army Materiel Development
Readiness Command. 1976.
“Engineering Design Handbook, Metric Conversion Guide, DARCOM P 706-470, Washington, DC.