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## PowerPoint Slideshow about ' College Physics' - linore

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Presentation Transcript

Measurements

- Basis of testing theories in science
- Need to have consistent systems of units for the measurements
- Uncertainties are inherent
- Need rules for dealing with the uncertainties

Systems of Measurement

- Standardized systems
- agreed upon by some authority, usually a governmental body

- SI -- Systéme International
- agreed to in 1960 by an international committee
- main system used in this text
- also called mks for the first letters in the units of the fundamental quantities

Basic Quantities and Their Dimension

- Length [L]
- Mass [M]
- Time [T]

Dimensional Analysis

- Technique to check the correctness of an equation
- Dimensions (length, mass, time, combinations) can be treated as algebraic quantities
- add, subtract, multiply, divide

- Both sides of equation must have the same dimensions

Operations with Significant Figures

- Accuracy -- number of significant figures
- When multiplying or dividing, round the result to the same accuracy as the least accurate measurement
- When adding or subtracting, round the result to the smallest number of decimal places of any term in the sum

Conversions

- When units are not consistent, you may need to convert to appropriate ones
- Units can be treated like algebraic quantities that can divide out
- See the inside of the front cover for an extensive list of conversion factors

How Fast is 1 m/s?

Order of Magnitude

- Approximation based on a number of assumptions
- may need to modify assumptions if more precise results are needed

- Order of magnitude is the power of 10 that applies

Cartesian coordinate system

- also called rectangular coordinate system
- x- and y- axes
- points are labeled (x,y)

Plane polar coordinate system

- origin and reference line are noted
- point is distance r from the origin in the direction of angle , ccw from reference line
- points are labeled (r,)

More Trigonometry

- Pythagorean Theorem
- To find an angle, you need the inverse trig function
- for example,

Slide 15

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