Notation, Units, and Rounding Numbers
Notation:

Book

By hand

Scalar 
a 
a 
Vector 
a (bold faced) 
a or _{} 
Units:


SI 

U.S. 

Mass 
M 
kilogram 
kg 
slug 

Length 
L 
meter 
m 
feet 
ft 
Force 
F 
Newton 
N 
pound 
lb 
Time 
T 
second 
s 
second 
sec 
Relation
between units is based on the equation F=ma:
1 N = (1 kg) (1 m/s^{2})
1
lb= (1 slug) (1 ft/sec^{2} )
Example
of calculating mass in U.S. system: The mass, m, of a particle which weighs
W=10 lb and is in a gravitational field of with an acceleration of gravity
g=32.2 ft/sec^{2} is
_{}
Unit
conversion:
l lb 
= 
4.4482 N 
1 slug 
= 
14.5938 kg 
1 ft 
= 
0.3048 m 
1 ft 
= 
12 in 
1 mile 
= 
5,280 ft 
1 kip 
= 
1,000 lb 
1 ton 
=

2,000 lb 
Rounding
numbers:
Round your final answers to 3
significant figures
_{}
Check
equations by checking that all terms in an equation have the same dimensions
ã Mehrdad Negahban and the
University of Nebraska, 19992000.
All
rights reserved
Copy
and distribute freely for personal use only
Department
of Engineering Mechanics, University of Nebraska, Lincoln, NE 685880526