Transcript Welcome to Chapter 1

Welcome to Chapter 1
AP PHYSICS
…do you remember…
• Theories
• Hypothesis
• Law
• Models
How about the SI system?...
• How big is
volts…that’s shocking!
• How small are cells?
Nano-nano
• Know your prefixes?
6
10
Significant Digits?
• What’s significant about that?
• Saved by zero?
• Scienctific ‘know’ tation?
• …know your sd rules?
Chapter 1…
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The scientific ‘methods’…
Decide on a problem…
Develop a hypothesis… If…then…
Test a hypothesis…experimentation…
Observe…record…conclude
Repeat until a hypothesis becomes a
theory…where do laws fit in?
Theory, Law, Principle…
• A theory explains how things work…
• …a theory can never be absolutely
proven.
• A law is a concise, but general statement
that describes how nature behaves…
• A less general statement is called a
principle…the line is a blur…
Measurement and Uncertainty
• Every measurement has
uncertainty…
• Estimated uncertainty is your +
or – number…
• Percent uncertainty is stated
as a %...
Significant Digits
• Non-zero numbers are always
significant…
• Trailing zeros left of a decimal are not
sd…
• Leading zeros to the right of a decimal
are sd…
• Trailing zeros to the right of a decimal
are sd…
• Sandwiched zeros are significant…
SI System
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The standard unit of length is the meter…
The standard unit of time is the second…
The standard unit of mass is the kg…
U is the unified atomic mass unit…
1u = 1.66 x10-27kg
MKS meter-kilogram-second system
Cgs is the centimeter, gram, second
system
Learn your prefixes…
•Know the prefixes on
page 11!!!
•Be able to convert
using steps or
powers…
Conversions/ Dimensional Analysis
• Simple units…
• Complex units…
• System to system
conversion factors…
Order of Magnitude
• O of M is a quick way to estimate values…
Yea!... Go do it…
• Home work …page 17
17-20, 23-26,30-33…
due next class BOP