PHY2048_08-26-09

# PHY2048_08-26-09 - Chapter 1 Measurement In this chapter we...

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Chapter 1 Measurement In this chapter we will explore the following concepts: 1. Measurement of a physical parameter 2. Units, Systems of units 3. Basic Units in Mechanics 4. Changing units 5. Significant figures

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What is Physics: Science of finding relations between different quantities Express these relations as a mathematical equation = Physical law Example: Ohm's law If we plot I versus V we get a straight line => The electric current is proportional to the applied voltage This is expressed in the form: The equation is known as: “Ohm’s Law” R is known as the “resistance” of the conductor Constant V R I Note: Electricity will not be discussed in this semester!
Units: For every physical parameter we will need the appropriate unit. Example: My bathroom scale showed 220 this morning. What would be the correct unit? A: Yd (Yards) (Unit for Length or Distance) B: kg (kilogram) (Unit for mass, but not the one used by the scale) C: m/s (meter per second) (Unit for velocity or speed, derived unit ) D: lbs (pounds) (Unit for mass used by scale) E: F (Fahrenheit) (Unit for Temperature) Different Units are often used for the same parameters (kg vs. lbs) Derived Unit : A unit which depends on other units For example: m/s depends on the definition of the meter and the second Fundamental Units : Units which depend on a standard!

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Fundamental Units = Base Quantities These parameters are: Length , Time, and Mass They are known as: Base Quantities Note: For the rest of the non-mechanical parameters we need to define only one more unit, that of the electric current In this book we use the International System of Units (SI) In this system the units for the base quantities are: Parameter Unit Name Symbol Length meter m Time second s Mass kilogram kg
A C B earth equator The meter In 1792 the meter was defined to be one ten- millionth of the distance from the north pole to the equator. For practical reasons the meter was later

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## This note was uploaded on 02/12/2010 for the course BCN 1210 taught by Professor Fobair during the Spring '09 term at University of Florida.

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PHY2048_08-26-09 - Chapter 1 Measurement In this chapter we...

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