Welcome To Physics

Welcome To PhysicsWhat is Physics?Physics is the study of matter and energy.

Imagine that the gods are playing some great game. Let's say a chess game. And you don't know the rules of the game. But you're allowed to look at the board, at least from time to time, and at a little corner perhaps. And from these observations you try to figure out what the rules are of the game Richard FeynmanHow do we study this?The scientific method. Four Steps:ObserveHypothesisExperimentAnalyzeYouve probably seen something like this:

Scientific MethodIn reality it is more like this:

ExperimentsControl vs. Experimental GroupIndependent vs Dependent VariableBlindTest subjects dont know the experimental and control groups.Placebo EffectDouble BlindSimilar to a blind experiment however the person administering the test is also unaware of the control and experimental groupsExampleJimmy Physics is driving to work. He reasons that by taking a shortcut he can cut down on his commute. Therefore, he times from when he leaves his house to when gets to work using the shortcut.To make sure it wasnt just a fluke he has his friend Albert drive along his normal route at the same time.After looking at his times he sees that this shortcut did in fact save him time. He got to work 3 minutes before Albert did.Example Cont.Give examples from the story that describe each step of the scientific method.What was the independent variable? The dependant?What was the experimental group? The control?Was this experiment Blind?Significant DigitsNonzero #s are always significant

3493 sig figs16394 sig figs

Significant DigitsLeading Zeros are never significant0.00552 sig figs0.00000003933 sig figs

Captive Zeros are always significant59084 sig figs21000047 sig figsSignificant DigitsTrailing Zeros are significant IFthere is a decimal point in the #8001 sig fig29002 sig figs

800.04 sig figs2900.4 sig figsOperations with Sig FigsMultiplication/Division rule:Retain the same number of sig figs in the answer as the factor containing the least number of sig figs.

4.5 x 2 = 9.0 rounds to 92000 x 21 = 42000rounds to 4000011 x 3 x 212 = 6996 rounds to 7000

Operations with Sig FigsAddition/Subtraction RuleLeave the answer rounded to the same precision (same decimal place) as the least precise number involved in the operation.

2 + 2.3 = 4.3 rounds to 4120 + 11 = 131 rounds to 1301.65 + 3 2.90 = 1.75 rounds to 2Sig Fig Examples#1: 23.0 4.25+ 25,620

#2:.00023 316Examples Solutions#1: 23.0 4.75+ 25,620 25,647.75rounds to 25,650#2:.00023 2sf 3163sf=.000000727rounds to .00000073Sig Fig Situation #1: Lets Not But Say We DidDont worry about rounding combo problems until all the work in the calculator is done, but heed the rules as if you did to find out # of digits needed in the end:(3.5 + 2.9454) / 357 = (6.4454)/357= 0.018054341Rounding: addition to tenths digit, which would leave 2 sig figs. 2 sig figs divided by 3 sig figs leaves 2 in answer: 0.018Sig Figs Situation #2: Exact #sWhenever a quantity has no uncertainty, it does not affect the # of sig figs in answer if x//+/-

Ex: four sides of a squareif one side has a length of 2.0 m, then 4 (exact #) x 2.0 m = 8.0 m (retain two sig figs cause exact # doesnt matter to sig fig roundingSig Figs Situation #3: Units!Units are to be treated in the same algebraic sense as variablesUnits do not affect sig figs but must be common to add/subtract values23 g + 32.00 g = 55.00 rounds to 55 g23 g x 32.00 g = 736.0000 rounds to 740 g223 kg + 27 ml cannot be simplified