Chapter 1: Introduction Physics

Opening Activity:

Write on the board any unit ofmeasurement.

Standards of Measurement

There are many different systems of measurement.

A standard is needed to be able to effectively share results of one experiment to anyone

This class will use the SI (Systeme International) system of measurement

*Fun Fact: USA invented the SI system and are one of only three countries that don’t use it. (Liberia and Myanmar being the other two.)

Standards of Measurement

The standard unit of measurement is the meter In 1799 the meter was defined as the one millionth

the distance from the equator to the North Pole In Until 1960s the official “meter” was the distance

between two lines on a piece of platinum-iridium alloy It is now defined as the distance light travels in

3.333e-9 seconds

Length

The standard unit for Mass is Kilogram Defined as the mass of a specific platinum iridium

alloy cylinder kept at the International Bureau of Weights and Measures at Sevres, France.

Mass is defined as the resistance to acceleration of an object introduced to a force

*Important Note: The SI unit for mass is NOT grams. ** Important Note: An objects mass is NOT its weight.

Mass

The standard unit for time is the second. Based on the frequency of light radiating from

a cesium-133 atom One second = 9 192 631 700 radiations

Time

Some values of large objects or time spans are approximated (Radius of earth, Age of Universe) These estimations are located on page 3 as

well as the front and back covers of your text

Approximate Values

Matter is made up of atoms Atoms are made up of a nucleus and an electron

cloud surrounding said nucleus Each different element has a differing number of

protons in said nucleus (along with neutrons) The electrons, neutrons and protons are made up

of 6 particles called Quarks The variation of elements compose different

types of matter and the amount of atoms directly affects an objects mass

Building Blocks of Matter

Technique used in order to approximate or to check a equation based on the units of the individual quantities Dimensions of equal magnitude can be

combined as if they were algebraic quantities

*Note that this technique should be used to check as it is not able to completely create an equation due to constants

Dimensional Analysis

Convert all properties into the three basic classifications of measurement Length (L) Time (T) Mass (M)

After performing all algebra convert the classifications to SI units

Steps

SI Units for the following: Area Volume Velocity is Acceleration is is

SI Units for Area, etc

Which of the following equations are feasible?

Δx=

Δx=

Δx=

Example

Show the expression is dimensionally correct, where and represent velocities, represents acceleration and represents a time interval.

Example

Significant Figures: A reliably known digit When multiplying two number the significant

figures in the quotient is the same as the number with the fewer significant figures.

When adding two numbers the sum with have the same number of decimal places as the number with the fewest decimal places.

*Note that rounding can cause a difference in the last sig fig between your answer and that in the back of the book

Uncertainty in Measurement

Several Carpet Installers make measurements for carpet installation in the different rooms of a restaurant. Compute the areas for the banquet hall, the meeting room and the dining hall taking into account sig figs. What total area of carpet is required for these rooms?

Example

Length (m) Width (m)Banquet Hall 14.71 7.46Meeting Room 4.822 5.1Dining Room 13.8 9

When using an equation all quantities must be converted into SI units. This includes both internally in the metric

system as well as from one system of measurement to another.

1mile = 1609 m 1ft = 0.3048 m1m = 39.37in 1in = 2.54 cm

Conversion of Units

Units can be treated as algebraic quantities that can “cancel” each other. Making a fraction with the conversion that will cancel the units we don’t want will allow s to accurately convert one quantity to another

= 38.1cm

Process

Convert using multiple conversion factors: If a car is traveling at a speed of 28.0 m/s is the driver exceeding the speed limit of 55.0 mi/h?

Example

The traffic light turns green and the driver of a fancy sports car slams the accelerator to the floor. The accelerometer registers 22.0 m/Convert this reading into km/

Example

Sometimes knowing an exact number for something is impossible

It is alright in these situations to estimate to a factor of 10 that is close.

Order of Magnitude

How many dollar bills would it take to reach the moon stacked one on top of another? Estimations say that 10 bills would be

approximately one mm. The distance to the moon is 4e5km away from

the earth.

Example

Two types of coordinate systems Cartesian (x,y) Polar (r, θ)

Graphing

Read the problem Draw a diagram Label all physical quantities Identify the values and list them in a chart Choose your Equation(s). Solve the equations for the unknowns Substitute in known values Check the answer if time allows

*all odd numbered problems are answered in the book

Problem Solving Strategy