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# Physics Chapter 1,2

## on Sep 05, 2008

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## Physics Chapter 1,2Presentation Transcript

• 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.
• Steps
• Recognize the problem
• Make observations; facts are verified observations
• Form a hypothesis – an educated guess
• Devise experiments to test the hypothesis
• 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/cm 3
• The Metric System The Comfort Zone m c d grams liters meters dk h k Milli Centi Deci Base Unit Deca Hecto Kilo
• Non-Comfort Zone p n µ m c d grams meters liters dk H K M G T pico Nano Micro Milli Centi Deci Base unit Deca Hecto Kilo Mega Giga Tera
• Scientific Notation
• Scientific notation expresses a number in exponential form (m x 10 n ) where 1≤m<10 and n is an integer.
• Examples of Scientific Notation
• 145
• 0.0078
• 42.7 x 10 4
• 89.6 x 10 -5
• 1.45 x 10 2
• 7.8 x 10 -3
• 4.27 x 10 5
• 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
• Which Group is more accurate?
• Group B
• Which Group is more precise?
• Group A
• Significant Figures
• Rules for Sig Figs
• Non zero digits are significant
• Final 0’s after the decimal are significant
• Zeros between 2 sig figs are significant
• 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
• They must be like terms (same units and same power)
• Always take care of the units first then get the powers to be the same (as one gets bigger the other gets smaller)
• Multiply Rules
• Multiply the bases and add the exponents.
• Make sure you use the correct units (Ex: m 2 )
• Divide Rules
• Divide the bases and subtract the exponents
• 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/Divide using Scientific Notation and Sig Figs
• 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 graphs
• Linear Relationship (straight line) y=mx + b
• Quadratic Relationship (parabola) y =kx 2
• Inverse Relationship (hyperbola) y = k/x
• Linear Graph Y = mx + b
• Quadratic or Parabola Y = kx 2
• Inverse or Hyperbola Y = k/x