Unit 1, Chapter 2

Foundations of Physics

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Unit 1: Measurement and Motion

• 2.1 Distance and Length• 2.2 Time• 2.3 Mass, Matter and the Atom

Chapter 2: Measurement and Units

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Chapter 2 Objectives1. Express lengths in metric and English units.2. Convert distances between different units.3. Calculate the surface area and volume of simple

shapes.4. Describe time intervals in hours, minutes, and seconds.5. Convert time in mixed units to time in seconds.6. Describe two effects you feel every day that are

created by mass.7. Describe the mass of objects in grams and kilograms.8. Use scientific notation to represent large and small

numbers.

2.1 Distance and Length

Key Question:How do we accurately communicate length and

distance?

*Students read Section 2.1 AFTER Investigation 2.1

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Chapter 2 Vocabulary Terms

• meter• centimeter• millimeter• kilometer• inch• foot mile• surface area• volume• weight

metric system conversion

factor time interval precision accuracy kilogram gram mass English system

atom inertia molecule mixture element base power of ten exponent scientific

notation distance length

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2.1 Distance and Length

measurement -

— a quantity and a unit

distance -

— is a length

— the amount of space between two points

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2.1 Two Systems of Units

Science problem solving requires both:

—Metric system

—English system

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2.1 Units of Length

• The common units of measurement in the English system are inches, feet, yards, and miles.

• These four length units are related to the meter.

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2.1 Convert Units

• conversion factor - – is the number by which you

multiply or divide a quantity in one unit to express the quantity in a different unit.

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2.1 Convert length

• A football field is 100 yards long.• What is this distance expressed in meters?

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2.1 Surface Area vs. Volume

surface area -— is the

measurement of the extent of an object’s surface or area without including its thickness.

volume -

— is a measure of the space occupied by a object.

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2.1 Calculate surface area and volume

A basketball has a radius of 12.5 centimeters. Calculate the surface area and volume of the ball.

1. You are asked to find surface area and volume.2. A ball is shaped like a sphere and you are given the radius.3. Surface area: A = 4πr2; volume: V = (4/3)πr34. Solve...

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2.2 Time

Key Question:How do we measure and describe time?

*Students read Section 2.2 AFTER Investigation 2.2

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2.2 Time

• Two ways to think about time:– What time is it?

• 3 P.M. Eastern Time on April 21, 2004,

– How much time has passed?• 3 hr: 44 min: 25 sec.

• A quantity of time is often called a time interval.

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2.2 Converting Mixed Units

1. You are asked for time in seconds.2. You are given a time interval in mixed

units.1 hour = 3,600 sec 1 minute = 60 sec

3. Do the conversion:1 hour = 3,600 sec26 minutes = 26 × 60 = 1,560 sec

4. Add all the seconds:t = 3,600 + 1,560 + 31.25 = 5,191.25 sec

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2.2 Time Units

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2.2 Accuracy and Precision

• accuracy– is the quality of being exact and free from error.– how close a measurement is to the true value.

• precision– is the degree of mutual agreement among a series of

individual measurements, values, or results.

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2.3 Mass, Matter and the Atom

Key Question:How is mass described?

*Students read Section 2.2 AFTER Investigation 2.3Physics World 18

2.3 Mass, Matter and the Atom

• Mass – is the amount of “stuff” an object contains.

• Two effects mass has on matter:– weight

• is the force of the Earth’s gravity pulling down. • Gravity acts on an object’s mass.

– inertia• is the tendency of an object to resist changes in

motion.• Inertia comes from mass.

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2.3 Measuring Mass

• kilogram -– is the mass of 1 liter of

water or 1,000 cubic centimeters of water.

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2.3 Scientific Notation

• Scientific notation works by expressing very small or very large numbers as the product of two numbers that are individually much easier to deal with. – The first number is called the base. – The second number is a power of ten.– The base is usually written with only one digit in

front of the decimal point.• ex. 2,500 would be written 2.5 × 103

– The small numeral 3 in 103 is called the exponent.Physics World 21

2.3 Mass, Matter and the Atom

• atom -– the smallest particle of an

element that can exist alone or in combination with other atoms.

• element– composed of all of the same

kind of atom.

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2.3 Mass, Matter and the Atom

• molecule -– is a neutral group of atoms that are chemically bonded

together; it is the smallest particle of a compound that can exist by itself and retain the properties of the compound.

• mixture -– is a substance that contains a combination of different

compounds and/or elements and be separated by physical means.

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2.3 Mass, Matter and the Atom

• The three most common forms of matter are called solid, liquid, and gas.

• At temperatures greater than 11,000 °C the atoms in a gas start to break apart and form plasma.

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2.3 Mass, Matter and the Atom

• Solids - Atoms in a solid stay together because the energy per atom is too low to break the bonds between atoms.

• Liquids- Liquids flow because atoms have enough energy to move around by temporarily breaking and reforming bonds with neighboring atoms.

• Gases- Gas atoms have enough energy to completely break bonds with each other.

• Plasma- In plasma, matter becomes ionized as electrons are broken loose from atoms.

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Application: Nanotechnology

miniature cell pump micro T.V. mirrors smaller

than insect legs

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More Here

http://ap-physics.david-s.org

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