Introduction to Physics Topics: 1. What is Physics 2. Units of Measure 3. Significant Figures 4. IV/DV 5. Math Review 6. Accuracy and Precision.

Introduction to Introduction to PhysicsPhysics

Topics:Topics:1.1. What is PhysicsWhat is Physics

2.2. Units of MeasureUnits of Measure3.3. Significant Figures Significant Figures

4.4. IV/DVIV/DV5.5. Math ReviewMath Review

6.6. Accuracy and PrecisionAccuracy and Precision

What is Physics?What is Physics?

Physics studies the physical Physics studies the physical relationships between objects.relationships between objects.

Physics studies topics ranging from Physics studies topics ranging from friction to molecular structure to friction to molecular structure to planetary motion.planetary motion.

Physics has been around as long as Physics has been around as long as people have been able to ask, “why people have been able to ask, “why does this happen?”does this happen?”

Beginning of Physics StudyBeginning of Physics Study

Greeks some of the first to document Greeks some of the first to document and study physics formally.and study physics formally.

Aristotle thought everything was Aristotle thought everything was made up of combinations of four made up of combinations of four elements: earth, fire, water, and air.elements: earth, fire, water, and air.

Physical properties of materials could Physical properties of materials could be explained by reasoning related to be explained by reasoning related to these four elements.these four elements.

Greeks con’tGreeks con’t

Why does smoke rise in the air?Why does smoke rise in the air? According to the Greeks, smoke rose into the According to the Greeks, smoke rose into the

air because it was made up of air and it will air because it was made up of air and it will always try to get back to its natural state.always try to get back to its natural state.

In addition, smoke rose to move away from In addition, smoke rose to move away from the earth and water.the earth and water.

Situations like this are how the Greeks Situations like this are how the Greeks explained natural events using early physics.explained natural events using early physics.

What topics are covered in What topics are covered in Physics?Physics?

Projectiles (think baseball, football, golf, etc)Projectiles (think baseball, football, golf, etc) Heat and frictionHeat and friction Forces (pulling and pushing objects)Forces (pulling and pushing objects) Energy (stored energy and energy of motion)Energy (stored energy and energy of motion) Momentum (think a small car colliding with a Momentum (think a small car colliding with a

large truck, who wins?)large truck, who wins?) Sound and lightSound and light Electricity and magnetismElectricity and magnetism

Units of MeasureUnits of Measure What system of measurement do we What system of measurement do we

use in the United States?use in the United States? By convention, we use the English System, By convention, we use the English System,

which has units like the inch, pound, which has units like the inch, pound, gallons, and Fahrenheit to name a few. gallons, and Fahrenheit to name a few.

•What system of measurement do most countries around the world use?

•The metric system is used by many countries, and this system has units like gram, meter, and centigrade (Celsius).

What units are used in What units are used in Physics?Physics?

We will be using SI units (SystWe will be using SI units (Systèème me Internationale - it’s French)Internationale - it’s French)

These units seem to overlap with the These units seem to overlap with the metric units, but there are some key metric units, but there are some key differences.differences.

Common Units Common Units Base Quantity

SI Base Unit & Symbol

Metric Base Unit

English Base Unit

Length Meter (m) Meter (m) Foot (ft)

Mass Kilogram (kg) Gram (g) Slug

Time Second (s) Second (s) Second (s)

Temperature Kelvin (K) Centigrade C

Fahrenheit (F)

Amount of a substance

Mole (mol) Mole Mole

Electric Current

Ampere (A) Ampere Ampere

Luminous Intensity

Candela (cd) Candela Candela

Conversion FactorsConversion Factors

1 inch= 2.54 cm1 inch= 2.54 cm 1 mile= 1.61 km1 mile= 1.61 km 1 gallon = 3.79 Liters1 gallon = 3.79 Liters 1 kg= 2.21 pounds (lbs)1 kg= 2.21 pounds (lbs) 1 calorie= 4.184 Joules1 calorie= 4.184 Joules 1 foot= 12 inches1 foot= 12 inches 3 feet= 1 yard3 feet= 1 yard 1 mile = 5280 feet1 mile = 5280 feet 1 meter = 3.28 feet1 meter = 3.28 feet 1 gallon= 4 quarts1 gallon= 4 quarts 1 pint= 32 tablespoons1 pint= 32 tablespoons 1 tablespoon =3 1 tablespoon =3

teaspoonsteaspoons 1 m1 m22= 10,000 cm= 10,000 cm22

1 minute= 60 seconds1 minute= 60 seconds1 hour= 60 minutes1 hour= 60 minutes1 eV=1.602 X 101 eV=1.602 X 10-19-19 J J1 light year = 9.46 x 101 light year = 9.46 x 101515 meters meters1 horsepower= 746 Watts1 horsepower= 746 Watts

Significant FiguresSignificant Figures

When given a long number, which of When given a long number, which of those digits are significant? those digits are significant?

Simple rules to remembering Simple rules to remembering significant figures.significant figures.

Sig Fig rulesSig Fig rules

#1: Non-zero digits are always #1: Non-zero digits are always significant!significant!

Ex 1: 635 has 3 significant figuresEx 1: 635 has 3 significant figures

#2: All #2: All finalfinal zeroes after the decimal zeroes after the decimal point are significantpoint are significantEx 1: 2.34000 has 6 significant Ex 1: 2.34000 has 6 significant figuresfiguresEx 2: 4.00 has three significant Ex 2: 4.00 has three significant figuresfigures

Significant Figure Rules, Significant Figure Rules, Con’tCon’t

#3: Zeroes between two other #3: Zeroes between two other significant figures are always significant. significant figures are always significant. Ex 1: 3005 has 4 significant figuresEx 1: 3005 has 4 significant figures Ex 2: 201 has three significant figuresEx 2: 201 has three significant figures

#4: Zeroes used solely as placeholders are not significant.Ex 1: 0.003 has one significant figure Ex 2: 0.1 has one significant figure

Examples: How many Examples: How many significant figures in the significant figures in the

following?following? A: 389A: 389 B: 389.00B: 389.00 C: 105.03C: 105.03 D: 105.030D: 105.030 E: 0.0003040E: 0.0003040 F: 11504F: 11504 G: 34.022G: 34.022 H: 0.44H: 0.44 I: 3.077I: 3.077

A: 3B: 5C: 5D: 6E: 4F: 5G: 5H: 2I: 4

Arithmetic with Significant Arithmetic with Significant FiguresFigures

In addition or subtraction the answer cannont In addition or subtraction the answer cannont contain more places after the decimal point that contain more places after the decimal point that the smallest number of decimal places.the smallest number of decimal places. Ex: 23.112233 + 1.3324 + 0.25= 24.694633Ex: 23.112233 + 1.3324 + 0.25= 24.694633

Since the fewest number of places after the decimal is Since the fewest number of places after the decimal is two, the answer is rounded to two decimal places, 24.69two, the answer is rounded to two decimal places, 24.69

In multiplication and division, the answer cannot have In multiplication and division, the answer cannot have more significant figures than the number being more significant figures than the number being multiplied or divided with the least number of multiplied or divided with the least number of significant figures.significant figures.

Ex: 23.123123 x 1.3344 = 30.855495Ex: 23.123123 x 1.3344 = 30.855495Since the fewest number of significant figures is 5, the Since the fewest number of significant figures is 5, the

answer answer must have 5 significant figures. Round the answer must have 5 significant figures. Round the answer to 30.855to 30.855

Independent and Dependent Independent and Dependent VariablesVariables

In science, it is important to know the In science, it is important to know the difference between these two because one difference between these two because one is a function of the other.is a function of the other.

If the independent variable changes, the If the independent variable changes, the dependent variable must also change.dependent variable must also change.

The independent variable is typically The independent variable is typically (although not always) the one that the (although not always) the one that the experimenter changes. experimenter changes.

The independent variable is also the The independent variable is also the variable that changes and controls the variable that changes and controls the outcome of the other. outcome of the other.

IV/DV con’tIV/DV con’t The relationship between the The relationship between the

independent and dependent variables independent and dependent variables is called a function.is called a function.

Ex 1: The longer you walk, the greater Ex 1: The longer you walk, the greater the distance from where you started.the distance from where you started. In this example, the independent variable In this example, the independent variable

is the time walking, and the dependent is the time walking, and the dependent variable is the distance from the starting variable is the distance from the starting point. We can say that the distance point. We can say that the distance covered is a function of time.covered is a function of time.

IV/DV con’tIV/DV con’t

Ex 2: Money earned and hours worked. Ex 2: Money earned and hours worked. In this example, the amount of money In this example, the amount of money

you earn depends on the number of you earn depends on the number of hours you worked. So the independent hours you worked. So the independent variable is the hours worked and the variable is the hours worked and the dependent variable is the money dependent variable is the money earned. Money earned is a function of earned. Money earned is a function of the hours worked.the hours worked.

IV/DV RelationshipsIV/DV RelationshipsIndependent and dependent variables Independent and dependent variables

exist in relationships with one another. exist in relationships with one another. Direct relationship: Both variables Direct relationship: Both variables

increase; on a graph, this line would increase; on a graph, this line would have a positive slope.have a positive slope.

Indirect relationship: One variable Indirect relationship: One variable increases, the other decreases; on a increases, the other decreases; on a graph, this line would have a positive graph, this line would have a positive slope. This is also called an inverse slope. This is also called an inverse relationship.relationship.

IV/DV RelationshipsIV/DV Relationships Exponential relationship: one variable Exponential relationship: one variable

increases or decreases exponentially increases or decreases exponentially while the other increases at a constant while the other increases at a constant rate.rate.

Oscillating relationship: variables Oscillating relationship: variables increase and decrease about each other.increase and decrease about each other.

Exponential Relationship Oscillating Relationship

Math ReviewMath Review

Right triangles: All triangles have Right triangles: All triangles have three angles that add up to 180 three angles that add up to 180 degrees. degrees.

In a right triangle, one of those In a right triangle, one of those angles must be 90 degrees, with the angles must be 90 degrees, with the last two adding up to 90 degrees. last two adding up to 90 degrees.

Right TrianglesRight Triangles SOH CAH TOA: Used to determine SOH CAH TOA: Used to determine

values of a leg, hypotenuse, or angle values of a leg, hypotenuse, or angle in a right triangle. in a right triangle.

Sin Sin ΘΘ= Opposite/Hypotenuse= Opposite/Hypotenuse Cos Cos ΘΘ= Adjacent/Hypotenuse= Adjacent/Hypotenuse Tan Tan ΘΘ= Opposite/Hypotenuse= Opposite/Hypotenuse