Welcome to Chapter 1

AP PHYSICS

…do you remember…

• Theories

• Hypothesis

• Law

• Models

How about the SI system?...

• How big is 106 volts…that’s shocking!

• How small are cells? Nano-nano

• Know your prefixes?

Significant Digits?

• What’s significant about that?

• Saved by zero?

• Scienctific ‘know’ tation?

• …know your sd rules?

Chapter 1…

• 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

• 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