Intro to Physics Mr. Kevin Bywaters

Modeling No we’re not selling clothes We’re describing motion etc, with equations…models

An object falling

Linear Motion d=d 0 + vt + ½ at2 v=v 0 + at  v 2 = v a  d a=  v/  t Force; F=ma Gravity:F=GmM/r 2, PE=-GmM/r, g=GM e /R e 2 Circular motion: v t =2  r/T=  r  =2  /T a c =  2 r=v t 2 /r a t =  r  =d  /dt Just a sampling of your new puzzle pieces!

Given r, T, and G solve for M

Equations Describe observed physical properties They do not explain why Once you properly choose appropriate equations to solve for unknowns, the rest is MATH. –Be neat and orderly. –Be consistent with units. –Beware of the calculator. –Do your algebra first!

Dimensions How long, how far, how tall? Duration? How much stuff? Electric charge? Length, L Time, T Mass, M Charge, q What is the quality being measured?

Dimensional Analysis Is the answer you seek, measured in apples, or oranges? Example: You want to know your average speed for your road trip to Virginia Beach. You traveled 120 miles in 150 minutes. What should be the dimensions of your answer? If you came up with something other than L/T, check your algebra!

Example Average speed – miles per hour Looks like? L/T 120 miles / 2.5 hours

Units Meters, m Seconds, s kilograms, kg Coulombs, C Length, L Time, T Mass, M Charge, q What is the standard you are measuring with?

Summary Physics is fun! Equations are like puzzle pieces Algebra is your friend “Laws” are our explanation of how the world works