Lecture 2: Introduction to Physics 101
Chapter 1 :
• The Conversion of Units (1.3)
• Trigonometry (1.4)
• Scalars and Vectors (1.5)
Physics 101: Lecture 2, Pg 1
Length:
Distance
Radius of visible universe
To Andromeda Galaxy
To nearest star
Earth to Sun
Radius of Earth
Sears Tower
Football field
Tall person
Thickness of paper
Wavelength of blue light
Diameter of hydrogen atom
Diameter of proton
Length (m)
1 x 1026
2 x 1022
4 x 1016
1.5 x 1011
6.4 x 106
4.5 x 102
1.0 x 102
2 x 100
1 x 10-4
4 x 10-7
1 x 10-10
1 x 10-15
Physics 101: Lecture 2, Pg 2
Time:
Interval
Age of universe
Age of Grand Canyon
32 years
One year
One hour
Light travel from Earth to Moon
One cycle of guitar A string
One cycle of FM radio wave
Lifetime of neutral pi meson
Lifetime of top quark
Time (s)
5 x 1017
3 x 1014
1 x 109
3.2 x 107
3.6 x 103
1.3 x 100
2 x 10-3
6 x 10-8
1 x 10-16
4 x 10-25
Physics 101: Lecture 2, Pg 3
Mass:
Object
Milky Way Galaxy
Sun
Earth
Boeing 747
Car
Physics Student
Dust particle
Top quark
Proton
Electron
Neutrino
Mass (kg)
4 x 1041
2 x 1030
6 x 1024
4 x 105
1 x 103
7 x 101
1 x 10-9
3 x 10-25
2 x 10-27
9 x 10-31
1 x 10-38
Physics 101: Lecture 2, Pg 4
Conversion of Units

Example:
Distance Buffalo – Andromeda Nebula given in ly. What is the
distance in km ?
1. Conversion factor: 1 ly=9.5 x 1012 km
2. Insert conversion factor:
d= 2 x 106 ly = 2 x 106 x 1 ly = 2 x 106 x 9.5 x 1012 km
= 1.9 x 1019 km
Remember: 10a x10b = 10a+b
10a/10b = 10a-b
Physics 101: Lecture 2, Pg 5
Example:

Speed limit on german autobahn is 130 kmh. What is the
speed limit in mph ?
Physics 101: Lecture 2, Pg 6
Lecture 2, ACT 1
A very good fastball pitcher can throw the ball 100 mph.
What is the ball speed in m/s?
1 - 450 m/s
correct
2 - 45 m/s
3 - 0.045 m/s
Physics 101: Lecture 2, Pg 7
Dimensional Analysis

Dimension indicates the nature of a physical quantity or the type
of unit.
Example:
Dimension of distance is length : [L]
Unit of distance is m , km, miles, …
Note:
Dimensions of left-hand side and right-hand side of an
equation have always to be the same, e.g. when you start with
a quantity of dimension length you have to finish with one
of dimension length.
Powerful check of your computation !
Physics 101: Lecture 2, Pg 8
Example:

x= ½ a tn. Find n ?
Physics 101: Lecture 2, Pg 9
Trigonometry
Right angle:
Definition of sine, cosine and
tangent:
Sin q = ho/h
Cos q = ha/h
Tan q = ho/ha
Pythagorean Theorem: h2 = ho2 + ha2
Physics 101: Lecture 2, Pg 10
Example:

A certain mountain road is inclined 3.1 degrees with
respect to the horizon. What is the change in altitude (in
meters) of the car as a result of its traveling 2.90 km along
the road ?
Physics 101: Lecture 2, Pg 11
Scalars and Vectors
Physics 101: Lecture 2, Pg 12
Lecture 2:
•
•
•
•
Units
Dimensional Analysis
Trigonometry
Scalars and Vectors
I strongly suggest that you try the
example problems in the textbook.
If you have trouble with any of them, please
go to office hours for help!
Physics 101: Lecture 2, Pg 13