Intro to Physics

Mr. Kevin Bywaters

Modeling

• No we’re not selling clothes

• We’re describing motion etc, with equations…models

An object falling

Just a sampling of your new puzzle pieces!

2

2

2

GmMF

rF ma

va

rr

vT

Given r , T, and G solve for M

9

-11

6

r=3.83 x 10

G=6.67x10

T=2.36 x 10

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