Today's Objectives:: Statics, Units, Calculations & Problem Solving

STATICS, UNITS, CALCULATIONS & PROBLEM SOLVING
Today’s Objectives:
Students will be able to:
a) Identify what is mechanics / statics.
b) Work with two types of units. In-Class activities:
c) Round the final answer appropriately. • What is mechanics
d) Apply problem solving strategies. • System of units
• Numerical calculations
• Sample concept quiz
• Problem solving strategy
• Sample attention quiz
WHAT IS MECHANICS??
Branch of physical sciences concerned with the state of

rest or motion of bodies subjected to forces
Engineering Mechanics
Solid Mechanics Fluid Mechanics
Rigid Bodies Deformable Bodies
Statics Dynamics
What may happen if static's is not applied properly?
Basic Quantities
Length Mass
– meter – kilogram
– foot – slug
Time Force
– second – newton
– pound
Table 1-1 in the textbook summarizes these unit systems.
SI Units
1. Modern version of metric system.
2. Base units are length, time and mass,

meter (m), second (s), and kilogram
(kg)
3. Acceleration of gravity:
m
g  9.81 2
s
SI Units
4. Force is derived quantity measured in unit
called a newton
kg  m
1N 1 2
s
Prefixes for SI units
Exponential form Prefix SI
symbol
Multiple
1,000,000,000 109 giga G
1,000,000 106 mega M
1,000 103 kilo k
Submultiple
0.001 10-3 milli m
0.000001 10-6 micro 
0.00000001 10-9 nano n
U.S. Customary Units (fps)
1. Base units are length, time and force.

2. feet (ft), second (s), and pound (lb)
3. Acceleration of gravity:
g  32.2 ft 2
s
U.S. Customary Units (fps)
4. Mass is derived quantity measured

in a unit called a slug:
2
lb  s
1 slug  1
ft
COMMON CONVERSION FACTORS
• 1 ft = 0.3048 m
• 1 lb = 4.4482 N
• 1 slug = 14.5938 kg
Numerical Calculations
• Dimensional Homogeneity
• Significant figures
• Rounding off numbers

Dimensional Homogeneity
Each of the terms of an equation must be
expressed in the same units.
s = v t + 1/2 a t2
s is the distance (position) in meters
v is velocity in m/s
a is acceleration in m/s2
t is time in seconds
m = m/s  s + m/s2  s2 = m
Significant figures
A significant figure is any digit, including a zero,
provided it is not used to specify the location of the
decimal point for the number.
5604 has four significant figures

34.52 has also four significant figures
0.5 has one significant figure
We can express numbers using exponents:

400 = 0.4(103) [to one significant figure]
2550 = 2.55 (103) [to three significant figures]
0.00546 = 5.46(10-3) [to three significant figures]
Rounding off
In our calculations, rounding off of
numbers is permitted. However, the
number of significant figures cannot be
less than 3.
Examples:
2/3 = 0.667
Sin 40 = 0.643
Example:
Convert 2 km/h to m/s. How many ft/s is this?
SOLUTION:
Since 1 km = 1000 m and 1 h = 3600 s, the conversion
 
factors are arranged so that a cancellation of units can be applied.
2 km
h
2 h
km
 1000 m
km
1h
3600 s
numerator denominator
2000 m
2 km h   0. 555 5  0 . 556 m
s
3600 s
Recall that 1 ft = 0.3048 m
m m 1 ft  ft ft
0.556  0.556    1.824  1.82
s s  0.3048 m  s s
Examples
Hint: Mg is Mega gram

SAMPLE READING QUIZ
1. The subject of mechanics deals with what happens to a body

when ______ is / are applied to it.
A) magnetic field B) heat C) forces
D) neutrons E) lasers
SAMPLE CONCEPT QUIZ
Give the most appropriate reason for using three significant figures
in reporting results of typical engineering calculations.
A) Historically slide rules could not handle more than three
significant figures.
B) Three significant figures gives better than one-percent
accuracy.
C) Telephone systems designed by engineers have area codes
consisting of three figures.
D) Most of the original data used in engineering calculations do
not have accuracy better than one percent
SAMPLE ATTENTION QUIZ
For a static’s problem your calculations show the final answer as

12345.6 N. What will you write as your final answer?
A) 12345.6 N B) 12.3456 kN C) 12 kN
D) 12.3 kN E) 123 kN

Today's Objectives:: Statics, Units, Calculations & Problem Solving

Uploaded by

Copyright:

Available Formats

Today's Objectives:: Statics, Units, Calculations & Problem Solving

Uploaded by

Document Information

Original Description:

Original Title

Copyright

Available Formats

Share this document

Share or Embed Document

Sharing Options

Did you find this document useful?

Is this content inappropriate?

Copyright:

Available Formats

Today's Objectives:: Statics, Units, Calculations & Problem Solving

Uploaded by

Copyright:

Available Formats

STATICS, UNITS, CALCULATIONS & PROBLEM SOLVING

Branch of physical sciences concerned with the state of

Solid Mechanics Fluid Mechanics

Rigid Bodies Deformable Bodies

2. Base units are length, time and mass,

1. Base units are length, time and force.

4. Mass is derived quantity measured

• Rounding off numbers

5604 has four significant figures

We can express numbers using exponents:

Hint: Mg is Mega gram

1. The subject of mechanics deals with what happens to a body

For a static’s problem your calculations show the final answer as

You might also like