Physics Chapter 1and 2

Metrics, Scientific Notation, Significant Figures and Graphing

Physics

The study of matter and energy and how they are related

Scientific Method

• This is an organized way of determining how the universe works.

• Steps1. Recognize the problem2. Make observations; facts are verified observations3. Form a hypothesis – an educated guess4. Devise experiments to test the hypothesis5. Draw conclusions from your results and formulate a

theory. A theory provides a logical explanation for a certain body of facts.

• A theory can change with contradicting evidence.

Money Drop Demo

The Metric System

• This is a scientific system of measurement. It is called the SI System or the International System of Measurement.

• Based on powers of ten

• This system was created by French scientists around 1795

Units of the Metric System

• Fundamental Units – units used to describe the quantities of length, time, and mass

• Time – seconds• Length – meter• Mass - kilograms

• Derived Units – combinations of fundamental units

• Examples: m/s, mph, or grams/cm3

The Metric SystemThe Comfort Zone

Kilo Hecto Deca Base

Unit

Deci Centi Milli

k h dk grams

liters

meters

d c m

Non-Comfort Zone

Tera

Giga

Mega

Kilo Hecto Deca

Base unit

Deci

Centi Milli Micro

Nano

pico

T G M K H dk

grams

meters

liters

d c m µ n p

Scientific Notation

• Scientific notation expresses a number in exponential form (m x 10n) where 1≤m<10 and n is an integer.

Examples of Scientific Notation

• 145• 0.0078• 42.7 x 104

• 89.6 x 10-5

• 1.45 x 102

• 7.8 x 10-3

• 4.27 x 105

• 8.96 x 10-4

Accuracy vs Precision

• Accuracy – extent to which a measured value agrees with an accepted value

• Precision – degree of exactness to which a measurement can be reproduced, limited to the smallest division on a measurement scale

• The known density of copper is 8.9 g/ml

• Group A gets a value of 8.7 g/ml and Group B gets a value of 9 g/ml

1. Which Group is more accurate?

• Group B

1. Which Group is more precise?

• Group A

Significant Figures

• Rules for Sig Figs

1. Non zero digits are significant

2. Final 0’s after the decimal are significant

3. Zeros between 2 sig figs are significant

4. Zeros used solely for spacing the decimal are not significant

Examples of Sig Figs

1.03

0.000034

0.003

0.3

3.00

30

30.

3

300.10

300.01

3 sig figs

2 sig figs

1 sig fig

1 sig fig

3 sig figs

1 sig fig

2 sig figs

1 sig fig

5 sig figs

5 sig figs

Add/Subtract/Multiply/Divideusing Scientific Notation

• Add/Subtract Rules1. They must be like

terms (same units and same power)

2. Always take care of the units first then get the powers to be the same (as one gets bigger the other gets smaller)

• Multiply Rules1. Multiply the bases and add

the exponents.2. Make sure you use the

correct units (Ex: m2)• Divide Rules1. Divide the bases and

subtract the exponents2. Make sure you use the

correct units (m/s) Only convert units that can

be converted (Ex: meters cannot be converted to seconds, but they could be converted to cm)

Add/Subtract/Multiply/Divideusing Scientific Notation and Sig Figs

• When adding and subtracting round your final answer to the least precise value

• Ex: 5.25 +120.1 =125.35, but our final answer is:• 125.4• When multiplying or dividing your final answer

has the least number of sig figs as the values you are working with

• Ex: 25 x 5.0 = 125, but our final answer is:• 130

Graphing

• Independent Variable-the variable that is manipulated or can be changed: plotted on the x-axis

• Dependent Variable-result of the independent variable: plotted on the y-axis

3 Types of graphs1. Linear Relationship

(straight line) y=mx + b

2. Quadratic Relationship (parabola) y =kx2

3. Inverse Relationship (hyperbola) y = k/x

Linear Graph

Y = mx + b

Quadratic or Parabola

Y = kx2

Inverse or Hyperbola

Y = k/x