Phys. 211Fall Semester 2014

Dr. F. Amir

Course Overview

http://chem.winthrop.edu/courses

• Introductions• Syllabus• Class notes• Homework

No Cell phones or Computers are allowed in class

Phys. 211

• Chapter 1• What is Physics• Significant figures• Scientific Notation• Units

• Homework Assignment: Chapter 1: P.2,P.3, P.7, P.11, P.13,P.19,P.23,P.41

What is Physics (Science)?

•Make Observations of the natural world

•Build Models that fit the observations

Mathematical Models

Predict outcome based on initial conditions

Observation: important first step toward scientific theory; requires imagination to tell what is important

Theories: created to explain observations; will make predictions

Observations will tell if the prediction is accurate, and the cycle goes on.

No theory can be absolutely verified, although a theory can be proven false.

Significant Figures

• Non zero digits are always significant

Significant Figures

• 25.8 miles/hour • sure of the 25,

estimating the last digit

• 3 significant digits

Reading Significant Figures

• 0.0000453200

There are 6 significant figuresBetter rewritten as 4.53200x10-5

Zeros written to the right of the decimal point for the purpose of spacing are NOT significant.

Final or ending Zeros are significant.

Reading Significant Figures• Nonzero Digits are always significant• Zeros between significant figures are significant.

• Examples:409.8 s0.058700 cm950.0X 101 mL

Answer• In 409.8 s : all four digits are significant• In 0.058700 cm: the two zeros on the left are not significant,

they are used to place a decimal point, the numbers 5,8,7 are significant, and so are the two final zeros.

• In 950.0 X 101 ml: the final zero is significant since it comes after the decimal point. The zero at its left is also significant since it comes between two other significant digits, so the results is four significant figures.

Adding Significant Figures• 67.9 g + 0.002 g + 3.51 g = ?

• Sum (or difference) can’t be more precise than least precise quantity

• Answer: 71.4 gWhen you add or subtract you keep the decimal place of the least precise value.

Multiplying Significant Figures

• Distance = velocity x timeVelocity = 65.4mphTime = 4.2 hours

Distance=274.7 or 275 or 2.7x102 miles

When you multiply (or divide) you keep the number of significant figures that are equal to the quantity with the smallest number of significant figures.

Importance of Units

• The 165 million dollars Mars Polar Lander

www.nasa.gov

Units help you figure out equations

Speed in mph

Density in kg/m3

Units help you determine the correct solution

Units, Standards, and the SI System

Quantity Unit Standard

Length Meter Length of the path traveled by light in 1/299,792,458 second

Time Second Time required for 9,192,631,770 periods of radiation emitted by cesium atoms

Mass Kilogram Platinum cylinder in International Bureau of Weights and Measures, in Paris

Units, Standards, and the SI System

Units, Standards, and the SI System

Units, Standards, and the SI System

Units, Standards, and the SI System

These are the standard SI prefixes for indicating powers of 10. Many are familiar; yotta, zetta, exa, hecto, deka, atto, zepto, and yocto are rarely used.

Units, Standards, and the SI SystemWe will be working in the SI system, in which the basic units are kilograms, meters, and seconds. Quantities not in the table are derived quantities, expressed in terms of the base units.

Other systems: cgs; units are centimeters, grams, and seconds.

British engineering system has force instead of mass as one of its basic quantities, which are feet, pounds, and seconds.

Converting units1. Multiplying by 1 leaves a quantity

unchanged.

2. “1” can be represented as

3. Choose form for ‘1’ for which units match.

Converting units1. You're stopped by police for speeding

30.0 km/h over the speed limit on an Ontario highway. What is the speed in mph?

2. That'll be a $180 fine, plus a $35 victim surcharge and a $5 court fee ($220 in all) should you decide to plead guilty and settle out of court. (in Canadian Dollars). What is the fine in US dollars?

Converting units

1. 30.0 km/h =? 1 km = 0.6214 miles

2. $220 Canadian Dollars = ?1 US dollar = 0.97 Canadian

dollar