A Numbers Game

Working with numbers, units and measurements in Physics

Measurements have 2 parts

A ________and a_______!

Measure to the most finite level you can, and estimate one additional decimal place.

Use metric whenever possible.

Precision Vs. Accuracy• Accurate – nearness to a correct or

“known” value.

• Precise – how close your answers are to each other.

Scientific Notation

• Physics deals with a lot of very small and very large #s. We need a short hand way of working with them.

• Scientific Notation• 1. move decimal so that the # is between 1 and 10.• 2. count how many places you moved it ( this is your

exponent)• 3. Rewrite # and X 10^

– If you move the decimal to the left it is positive– If you move the decimal to the right it is negative

• How to enter in your calculator:Be careful when dividing! (use parenthesis)

Examples

• Write in scientific notation:

• 2340000000

• 34580000000000

• .0000456

Expand

3.45 X 10-5

6.79 X 104

SI system

• Mass – kg• Distance – m• Time – s• Temperature – K ( C)

• Derived units: density, area, velocity, volume

• 1 cm3 = 1 mL

Dimensional Analysis

• Set up Conversions = to one.• 1. Determine what unit is given, and which you

are seeking.• 2.Start with the unit given in the top ( usually)

left-hand side.• 3. Work across using conversions to cancel until

you get the unit you are seeking.• 4. Make sure your answer makes sense.• MORE DETAILED NOTES IN HANDOUT!

Dimensional Analysis Example

A note about problems

• …your #s are NOT usually nice and neat like they are in math class.

• Please round to 2 decimal places!