Class Notes 22 August HW: I often write common mistakes and advise here. Any trouble with WebAssign? #4 = units!, #6 = fun? Today: Units, prefixes, etc. Comments about doing HW Mechanics / Kinematics

Which is correct, considering sig figs? (74.50  2.2)/3.885 = ? 42.188 42.19 42.2 42 40 Some other number Answer d is correct. Keep the least number of significant figures. Here, that’s 2 in the 2.2 number.

Which is correct, considering sig figs? 27.1539 + 138.2 – 11.74 = ? 153.6 153.61 153.614 153.6139 Some other number Answer b is correct. Keep the least precise decimal place. Here, that’s 0.2 in the 138.2 number.

Chapter 1 Estimating an answer Dimensional Analysis Approximation Can use to check your answers E.g. Could you carry $10M in gold? Dimensional Analysis Make sure the units are correct If the units are not correct the answer can not possibly be correct! 1 once is $1000, 1 ounce is about 30 g. Roughly 300 kg or 600 pounds.

Système International (SI) Units are standards in terms of which measurements are stated. Seven units we must define. All else in terms of these. Interestingly, only 3 countries have not officially adopted the SI system: Liberia, Myanmar, and the USA! (possibly out-of-date. Hard to find out about the first two.)

Description SI symbol Length Meter m Mass Kilogram kg Time Second s Elec. Current Ampere A Temperature Kelvin K Amount Mole mol Luminous Intensity Candela cd s sec Note: The Ampere not the Amp. Use s for seconds not sec.

Système International (SI) Units are standards in terms of which measurements are stated. Seven units we must define. All else in terms of these. Conversions (multiply by 1!) Le SI d’Unites. Do conversion of units before prefix. For convenience, there can be prefixes assigned. You need to know these…

109 giga G 106 Mega M 103 kilo k 10-3 milli m 10-6 micro 10-9 nano n Power Prefix symbol 109 giga G 106 Mega M 103 kilo k 10-3 milli m 10-6 micro 10-9 nano n m (mu)

Have you ever had a physics course before? I have had a physical science course. Does that count? Man I took physics already and I’m going to rock your class! I have not had either physics or physical sci. d) I thought this was psychology?

Why are you in this class? It is a GSSM requirement and I really don’t want to take it? It is a GSSM requirement and I’m looking forward to this class. Whatever; I’m ambivalent. Mommy told me to do it.

Writes No pictures  unknown Didn’t skip a line b/w problems  Problems & name Writes unknown No pictures  Didn’t skip a line b/w problems  Write given values Write general equation Solves equation for unknown first Then enters values (without units  ) Answer highlighted

No equations, no diagrams, often no units during the calculations, answers are not boxed-in, etc…

Homework Read Chapter 2, sections 1-3 HW#03: Get it on Canvas  Turn in on paper, either with or without the sheet stapled to the front.