Physics

• What is Physics?

  • Physics is the branch of knowledge that studies the physical world

  • A mathematical science

  • The search for understanding

  • The study of matter and energy

    • Best Answer

• Who are Physicists?

  • Physicists are people who investigate the physical world

Science

• What is Science?

  • Knowledge, the act of knowing

• Who are Scientists?

  • People who look at the world around them with questioning eyes

  • They ask many questions

  • Hope for powerful explanations that describe more than one phenomenon and lead to a better understanding of the universe

Need for Scientist/Physicist

• To improve the standards of living

• To solve the many problems that we encounter

  • Require a common language for comparison of data

Scientific Method

• Greek philosophers (4th and 5th century BC)

  • Based their findings on observations and then fitting them into a logical framework or theory

• Europeans (16th Century)

  • At first they accepted the no experiment Greek philosophy

  • Galileo Galilei (1564-1642)

    • First scientist to publicly state that knowledge must be based on observations and experiments

    • To prove the Greeks wrong he developed a systematic method of observation, experimentation and analysis

    • The Father of the Scientific Method

Scientific Method

• Identify the problem

• Gather data

• Form a hypothesis

• Test hypothesis

• Form conclusion

• **Not only way to learn

Measurements (Need for a Common Language)

• English System - British System

• Metric System - S.I System

  • 1795 French scientist developed

  • Easy to Use

    • Based on powers of 10

    • Decimal System

  • Standards were determined by international committee because of need for worldwide standards

    • Standards for mass, length, volume and time are kept by N.I.S.T.

S.I. System Standards and Derived Units of Measurement

• Standard Units

  • Mass - Kilogram (kg)

    • The amount of matter in an object

  • Length - Meter (m)

  • Time - Second (s)

  • Volume - Liter (L)

    • How much space an object takes up

• Derived Units

  • Standard units used together to describe other quantities

    • Speed = distance / time = m / s

    • Density = mass / volume = Kg / L

    • Volume = length * width * height = m³

S.I Prefixes

• T G M K H D megs d c m µ n p

• Tera = T

  • 10¹²

• Giga = G

  • 10⁹

• Mega = M

  • 1,000,000 = 10⁶

• Kilo = K

  • 1,000 = 10³

• Hecto = H

  • 100 = 10²

• Decka = D, da, dk

  • 10

• Base Units

  • m, l, g, s

  • 1

• Deci = d

  • 1/10

• Centi = c

  • 1/100 = 10^-2

• Milli = m

  • 1/1,000 = 10^-3

• Micro = µ

  • 1/1,000,000 = 10^-6

• Nano = n

  • 10^-9

• Pica = p

  • 10^-12

Rules for Rounding

• If the digit to be dropped is 4 or less, just drop it

  • 21.3 → 21

  • 1.24 → 1.2

• If the digit to be dropped is 6 or greater, increase the digit to the left by one

  • 21.6 → 22

  • 1.26 → 1.3

• If the digit to be dropped is 5, increase the digit to the left if it is odd. Do not increase the number to the left if it is even

  • 21.5 → 22

  • 24.5 → 24

Scientific Notation

• Expressing large and small numbers in short hand method by expressing the decimal places as powers of 10

• M * 10ⁿ

  • M is the whole number and n is the power of 10

  • Examples of large numbers

    • 6,000,000,000,000,000,000,000,000 kg - Mass of Earth

      • 6 × 10²⁴ kg

    • 300000000 m/s - speed of light

      • 3 * 10⁸ m/s

  • Examples of small numbers

    • .000000000000000000000000000000911 kg - Mass of an electron

      • 9.11 * 10^-31 kg

Rules for Writing Scientific Notation

• Move the decimal point to get only one nonzero number to the left of the decimal

  • 1 <= M >= 9

    • The whole number must be between 1 and 9

  • 2,000 = 2 * 10³

  • .0003 = 3 * 10^-3

Scientific Notation Rules for Adding and Subtracting

• Numbers must have same units

• Numbers must have same power of 10

• Precision must be same (round)

• Add or subtract the whole number parts and include the common power of 10 and units

• Examples

  • 4 * 10⁸ m + 3 * 10⁸ m = 7 * 10⁸ m

  • 6.2 * 10^-3 m - 2.8 * 10^-3 m = 3.4 * 10^-3 m

  • 4.0 * 10⁶ m + 3.1 * 10⁵ m

    • 4.0 * 10⁶ m + 0.3 * 10⁶ m = 4.3 * 10⁶ m

Significant Figures

• Any measurement is inaccurate to some degree. The inaccuracy stems from several factors. The precision of any measuring device is limited. The person doing the measurement may introduce error. The experimental technique may be faulty. Because a measurement contains some degree of inaccuracy, the number of digits that are valid for the measurement are also limited.

• The digits which indicates the number of units we are reasonably sure of having counted in making a measurement are significant figures.

The more precise the instrument, the more significant figures you will have.

Significant Figure Rules

• All nonzero digits are significant

  • 3659 has 4 sig figs

• All zeros between two nonzero digits are significant

  • 406 has 3 sig figs

  • 4006 has 4 sig figs

• All zeros to the left of an understood decimal but to the right of a nonzero digit are not significant

  • 6000 has 1 sig fig

• All zeros to the left of an expressed decimal point and to the right of a nonzero digit are significant

  • 6000__.__ has 4 sig figs

• All zeros to the right of a decimal point but to the left of a nonzero digit are not significant

  • .0214 has 3 sig figs

• All zeros to the right of both the decimal point and a nonzero digit are significant

  • .021400 has 5 sig figs

• All numbers in front of the power of 10 in scientific notation are significant

  • 3.014 * 10^5 has 4 sig figs

Significant Figure Rules for Addition and Subtraction

• All measurements must be in the same units

• The answer obtained can not be any more precise than the least precise measurement used in the problem

  • Any measurement which has significant figures in a column of numbers which contains a non-significant figure should be rounded off until every number in a column is a significant figure

• Add or Subtract

  • Round before adding or subtracting

Significant Figure Rules for Multiplying and Dividing

• The answer can’t have more significant figures than the number in the problem having the least number of significant figures

  • 6.134 ft (4 sig figs) * 2.0 ft (2 sig figs) * 1.01 ft (2 sig figs) = 12 ft

    • Answer can only have 2 sig figs because it is the least number

Graphing

Graph

• a visual display of data that shows a relationship between the dependent and independent variables

• Dependent Variable - “Measure”

  • Changes based on the independent variable

• Independent Variable - “Control”

  • Is not affected by the dependent variable

• Slope

  • (y₂ - y₁) / (x₂ - x₁)

Relationships

• correlations between data on a graph

• Direct relationship

  • Both X and Y increase

  • Direct Linear

    • y = mx + b

  • Direct Power

    • y = mx²

  • Direct Root

    • y = m √x

• Indirect relationship

  • As X increases, Y decreases

  • Indirect Inverse

    • y = m/x

  • Inverse Power ( “Inverse Square” )

    • y = m / x²

  • Inverse Root

    • y = m / √x