MEASUREMENTWHAT IS PHYSICS

THE METRIC SYSTEM

METRIC PREFIXES

DIMENSIONAL ANALYSIS

SIGNIFICANT FIGURES

CONVERSION OF UNITS

ORDER OF MAGNITUDE

NOTATION

TRIGONOMETRY

P

P

P

P

P

P

P

P

P

Physics is the study of how physical quantities are related. It isconcerned with the understanding of the natural universe.

Physics is based on experimental observation.

Physics is organized into a set of physical laws havingmathematical expressions.

PHYSICS:Mechanics

Thermodynamics

Electromagnetism

Relativity

Quantum Mechanics

THE METRIC SYSTEM:

The fundamental physical quantities of the metricsystem are:

length, mass, and time.

Metric system basic units:

length: the meter

mass: the gram

time: the second

Metric prefixes are based on powers of 10.

prefix power abbreviation

tera 10 12 Tgiga 10 9 Gmega 10 6 Mkilo 10 3 K- 10 0 -milli 10 -3 m

micro 10 -6 nano 10 -9 npico 10 -12 p

MASS:

Mass in kg:

Universe 1052 (?)

Milky Way Galaxy 7x1041

Earth 6x1024

Human 7x101

Bacterium 1x10-15

Electron 9x10-31

Lengths and Distances in m:

Distance to most remote Quasar 1x1026

Distance to nearest Galaxy 1x1022

Distance to nearest Star 4x1016

Mean orbital radius of Earth 4x1011

Length of a housefly 5x10-3

Size of a living cell 1x10-5

Diameter of a proton 1x10-15

Time Intervals in s:

Age of Universe 5x1017

Age of earth 1x1017

Average of college student 6x108

One day 9x104

Period of audible sound wave 1x10-3

Period of visible light wave 2x10-15

Time for light to cross a proton 3x10-24

Dimensional Analysis:

Physical units combine algebraically .

a = acceleration [a] = L/T 2

x = distance [x] = L

t = time interval [t] = T

x = at2/2

L = (L/T2)T2 = L

EXAMPLE: Using the variables v and r for speed (meters per second) and distance (meters), combine them algebraically to form an acceleration, a (meters per second squared).

2va

r

EXAMPLE: Using the variables v and r for speed (meters per second) and distance (meters), combine them algebraically to form an acceleration, a (meters per second squared).

Significant Figures:

Significant figures includes the first estimated digit.

Multiplication or Division: 1. Calculate the result2. The result has the same number of significant

figures as the factor with the fewest.

Zeros immediately to the right of a decimal point are notsignificant unless they are by themselves.

Zeros on the end of a number (5200) may or may not besignificant. 5200. or 5.2x103

Adding and Subtracting: The result has the same numberof decimal places as the value with the fewest.

Conversion of Units:

All conversion factors begin with an equation: x = y.

All conversion factors are equal to 1 (unity).

If x = y, then x/y = 1 and y/x = 1.

Chose the ratio that eliminates the original unit.

100 cm = 1 m

52 cm = 52 cm x 1m/100cm = 0.52 m

EXAMPLE: Convert 67 miles per hour to meters per second.

1 mile = 1609 meters 1 hour = 3600 seconds

EXAMPLE: Convert 3525.00 cm2 to m2.

EXAMPLE: Convert 67 miles per hour to meters per second.

1 mile = 1609 meters 1 hour = 3600 seconds

EXAMPLE: Convert 3525.00 cm2 to m2.

67.00 mi/hr

1 mi

1609 m 1 hr

36 00 s

= 29.95 m/s

3525.00 cm2

(100 cm)2

(1 m)2

= 0.3525 m2

Order of Magnitude Calculation:

An order of magnitude calculation is done by selectingreasonable sized values to substitute into an equation. Thepurpose is to determine the size of the real calculation result.

EXAMPLE: How much tire tread is worn off a tire for every mile driven?

EXAMPLE: How much tire tread is worn off a tire for every mile driven?

A tire lasts about 40,000 miles and takes off about 1 cm of tread. Thus about 2.5x10-7 m/mile of tread is removed. The important value is the power of 10.

NOTATION:

means change in.

means sum of.

2 1 f ix x x or v v v

1 2 3 ...x x x x

Trigonometry:

c

b

a

sin sin

cos cos

tan

bb c

ca

a ccb

a

The trigonometric functions are most easily understood as ratios of the lengths of the sides of a right triangle.

2 2 2

1tan

c a b

b

a

Solve the triangle for the unknown sides.

40o

8

X= ______

Y= _____

Solve the triangle for the unknown sides.

40o

8

X= ______

Y= _____

6.128

5.142

Problem Solving:

Read the problem carefully.

Draw a diagram or sketch of the problem, don’t bean artist.

Identify given information.

Select basic relationship that applies.

Substitute data and calculate result.