1-1 what is physics? what does physics mean? "physics" is from the greek root physik...

1-1 What is Physics? What does Physics mean?"Physics" is from the Greek root physik (science of nature) and Latin physica (natural science). It’s the scientific study of matter, energy, force,

and motion, and the way they relate to each other.

Studies how things work in the material universe.

Chapter 1 The Science of Physics

http://www.youtube.com/watch?v=AEIn3T6nDAo&feature=youtu.be

Video – The Big bang tv show – “what is Physics?”

Physics explains things that are very, very large.

Physics explains things that are very, very small.

1-2 Measurements in ExperimentsScientific Notation Extremely large or small numbers are expressed in

powers of ten.6.02 x 1023

1.6 x 10-19Rules: When adding or subtracting numbers written in scientific notation exponents

must be the same. Move the decimal point to the left you add one to the exponent, when moving decimal point to the right you subtract one from exponent.

When dividing 2 numbers written in scientific notation subtract exponents. When multiplying 2 numbers – add exponents.

Example: 4.25 x 107 + 2.25 x 108

2.68 x 108 or 26.8 x 107 are equal – same value

Scientists use the International System of Units, or SI.

Common SI base Units:Length – meter (m)Mass – kilogram (kg) Time – second (s)Electric Current - ampere (A)Thermodynamic Temperature – kelvin (K)Amount of a substance - mole (mol)

Derived Units – units that came from a combination of other units

Example: Newton and speed1 kg / m/s2 and m/s

The Metric System

I’m ten times better than the Standard

system of measurement!”

Regardless of the unit, the entire metric system uses the same prefixes.

Some common prefixes:

• giga = Gx10+9 or billions

• mega = Mx10+6 or millions

• kilo = kx10+3 or thousands

• centi = cx10-2 or hundredths

• milli = mx10-3 or thousandths

• micro = x10-6 or millionths

• nano = nx10-9 or billionths

• pico = px10-12 or trillionths

To convert measurements use Dimensional Analysis by multiplying by a conversion factor: a factor equal to one.

Example: To convert 56 m to km -- 56 m x 1 km = 0.056 km 1000 m

Example: Convert 65 mph to km/hr

65 mi/hr x 1.61 km/hr1 mi /hr

= 104 km/hr

Conversion factor

Accuracy and Precision Accuracy – describes how close a measurement is to the

true value of the quantity measured. Precision – the exactness of a measurement Example: 45.052 m is more precise than 45.0 m

Low AccuracyHigh Precision

High AccuracyLow Precision

High AccuracyHigh Precision

Significant FiguresUsed to show the precision of a measured quantity Include all digits that are actually measured plus one estimated digit.

Rules: 1) All non zero numbers are significant

738 = 3 sig figs12345 = 5 sig figs

2) Zeros located between non-zero digits are significant 2014 = 4 sig figs

This measurement should be read as 4.95 cm. This measurement has 3 significant figures.

3) Trailing zeros (at the end) are significant only if the number contains a decimal point; otherwise they are insignificant (they don’t count)

1.00 = 3 sig figs549000. = 6 sig figs549000 = only 3 sig figs

4) Zeros to the left of the first nonzero digit are insignificant (they don’t count); they are only placeholders.

000.456 = 3 sig figs0.052 = 2 sig figs

Rules for addition/subtraction problems The number of decimal places in the result equals the number

of decimal places in the least precise measurement

Example: 7.939 + 6.26 + 11.1 = 25.299

Answer = 3 sig figs 25.3 (rounded up)

Rules for multiplication/division problemsThe number of sig figs in the result equals the number in the

least precise measurement used in the calculation

Example: (27.2 x 15.63) ÷ 1.846 = 230.3011918

Answer = 3 sig figs 230. (rounded down)

1-3 The Language of Physics Graphs and Charts Symbols

In Physics there are 3 types of mathematical relationships that are most common.

1) linear relationship (or direct relationship) expressed by the equation y = mx + b where m is the slope and b is the y-intercept

2) Another relationship is the quadratic relationship. The equation is y = kx2, where k is a constant.

3) The third equation is an inverse relationship, expressed by xy = k, where k is a constant.

Trigonometry will become important when we study vectors and parabolic motion

Way to remember trig functions: “SOH CAH TOA”