Transcript Phys 1111 K Spring 2004 - Georgia State University

Phys 1111K
Spring 2005
Course Overview
Dr. Perera
Room: 507 Science Annex
Phone: 651-2709, 3221/3222
1
Introduction
• What is Physics ?
Understanding nature
• Laws of Physics
Wide spread impact on modern technology
• Every minute of your life is involved in Physics
Needs and Uses Even without knowing it
• A Fundamental Science  Welcome to Introduction to
Physics
2
Main Sections
Kinematics
• Classical Mechanics (Chs 1-10)
both Transnational and Rotational Dynamics
• Fluid Mechanics (Ch 11)
• Thermodynamics (Chs 12-13)
Heat
Temperature
3
Ch 1 Pre Requisites
Co-ordinate System (Cartesian)
•
Trigonometry
Pythagorean Theorem
Sin θ
Cos θ
Pythagorean Theorem
Tan θ
•
Algebra
Quadratic Equations
Powers of 10
•
Symbols
Δx, μ, n, p
4
Standards and Units
Why do we need standard units ?
King Louis
• Yard
• Royal foot
CGS
British
SI
centimeter
(cm)
foot (ft)
meter (m)
Mass
gram (g)
slug (sl)
kilogram
(kg)
Time
second (s)
second (s)
second (s)
Length
5
SI Units
Le System International Units
• meter :
Light travels in a vacuum in time of 1/
299792458 seconds
• kilogram : Standard cylinder of Pl-Iridium alloy at
room temperature
• second :
Cs-133 atomic clock – time for
9192631770 wave cycles to occur
6
Conversion of Units
1 meter = 100 centimeter = 1000 millimeter (mm)
103 meter = 1000 meters = 1 kilometer
0.001 meter = 10-3 meter = 1 millimeter
3.281 feet = 1 meter
5280 feet = 1 mile
3600 seconds = 1 hour
0.65 miles / hour = 95 feet / second = 29 meters / second
7
Significant Figures
Keep the same number of significant figures in the
answer as in the least accurate number
3.5 × 10.6 = 37 (not 37.1)
0 ± 0.1
0 ± 0.1
35
39
Uncertainty : Quality of the apparatus
Skill of the experimenter
Number of measurements
8
Dimensional Analysis
•
Distance -
[L]
•
Mass
-
[M]
•
Time
-
[T]
Check whether an equation is mathematically
correct
Find an unknown exponent
9
Vectors and Scalars
•
Addition and subtraction
•
Multiplying by a number
•
Components
•
Vector addition by Components
•
Vector addition by Graphing
10
Vector Addition

(Due East)
Resultant Displacement
R = A+ B

Due East and then Due
north
R = A +B
5 = 4 +3 ?
Find Theta
11

What if Vectors are not
Perpendicular ?
Can we say R = A +B ?
But Pythagorean Theorem
valid ?
Graphical Technique
A = 275 m, B =125 m
Scale 1 cm = 10 m
R = 228 m
12
Vector Components
r=X+Y
r  A, X Ax Y AY
13
Different Axes
Vector Components depend
on the orientation of the
axes
Scalar components
(With positive or negative
sign)
14
Adding Vectors Using Components
C = A +B,
A = Ax +Ay
B = Bx + By
C = Cx + CY
CX =
CY =
15
Example 8
y
AX
BX
35
B
By
A
Ay
20
R
x
A+B=R
A=Ax+Ay
B=Bx+By
Note By is in negative direction.
16
Example 8 (continued)
x component
y component
A
Asin20=145sin20=49.6
Acos20=145cos20=136.3
B
Bcos35=105cos35=86.0
-Bsin35=-105sin35=-60.2
R
Ax+Bx=135.6
AY+BY=76.1
17
Example 8 (continued)
Ry
76.1m
)
  tan ( )  tan (
135 .6m
Rx
1
1
 29
0
18