1. WELCOME TO Physics 2425-300 Mr. Kris Byboth

2. Syllabus The course syllabus can be found on the web at The course syllabus can be found on the web athttp://www.blinn.edu/brazos/natscience/phys/kbyboth/

3. Keys To Success Don’t get behind Don’t get behind Ask a question every time something is unclear! Ask a question every time something is unclear! Write a formal solution to every problem (learn how to approach problems) Write a formal solution to every problem (learn how to approach problems) Work more problems (you cannot memorize physics) Work more problems (you cannot memorize physics) Form study groups Form study groups

4. What is Physics? Physics is the study of the laws of nature. Physics is the study of the laws of nature. It is the attempt to understand, model, and predict the behavior of the world around us. It is the attempt to understand, model, and predict the behavior of the world around us. This course will emphasize application of mathematical models to physical situations. This course will emphasize application of mathematical models to physical situations.

5. Units Each measurement requires some predefined unit of measure. Each measurement requires some predefined unit of measure. Units will often help you identify what variables are being given in a problem. Units will often help you identify what variables are being given in a problem.

6. QuantityDimensionSI UnitCGS UnitBE Unit LengthLmcmft MassMkggslug TimeTsss VelocityL/Tm/scm/sft/s AccelerationL/T 2 m/s 2 cm/s 2 ft/s 2 Force (F=ma)ML/T 2 N=kg∙m/s 2 (Newton) dyne=g∙cm/s 2 lb =slug∙ft/s 2 (pound) Work or Energy (W=Fd ) ML 2 /T 2 J=N∙m (Joule) erg=dyne∙cmft∙lb Power (P=W/t) ML 2 /T 3 W=J/s (Watt) erg/sft∙lb/s Pressure (P=F/A) M/(LT 2 )Pa=N/m 2 (Pascal) dyne/cm 2 lb/ft 2

7. SI Units Length meter (m) – The distance traveled by light in vacuum in 1/299,792,458 seconds Mass kilogram (kg) – The mass of a specific platinum-iridium cylinder Time second (s) – The period of 9,192,631,770 oscillations the radiation from a cesium-133 atom

8. Conversions Converting between units is just multiplying by one. Converting between units is just multiplying by one. 7.4ft = ?in 7.4ft = ?in The conversion factor is 1ft = 12 in The conversion factor is 1ft = 12 in

9. Conversion factors to know 1ft = 12 in 1ft = 12 in 1in = 2.54cm 1in = 2.54cm 1yd = 3ft 1yd = 3ft 1mi = 5280ft = 1609m 1mi = 5280ft = 1609m 1m = 3.281ft 1m = 3.281ft 1hr = 60min = 3600s 1hr = 60min = 3600s 1m = 100cm = 1000mm 1m = 100cm = 1000mm 1km = 1000m 1km = 1000m

10. Unit Prefixes PrefixAbbreviation Conversion PrefixAbbreviation Conversion megaM10 6 megaM10 6 kilok10 3 kilok10 3 centic10 -2 centic10 -2 millim10 -3 millim10 -3 microμ10 -6 microμ10 -6 nanon10 -9 nanon10 -9 picop10 -12 picop10 -12 Read as 1 (Prefix) = Conversion (unit) Read as 1 (Prefix) = Conversion (unit) 1kilometer = 10 3 m = 1000m 1kilometer = 10 3 m = 1000m 1cm = 10 -2 m = 0.01m 1cm = 10 -2 m = 0.01m

11. Conversion Practice 4.500yd = ? cm 4.500yd = ? cm 411.5cm 411.5cm 45m 2 = ? cm 2 45m 2 = ? cm 2 4.5∙10 5 cm 2 4.5∙10 5 cm 2 55.0mi/hr = ? m/s 55.0mi/hr = ? m/s 24.6m/s 24.6m/s

12. Significant Figures An easy way to maintain accuracy in calculations. An easy way to maintain accuracy in calculations. All non-zero numbers are significant All non-zero numbers are significant Zeros are not significant if they are leading (0.003). Zeros are not significant if they are leading (0.003). Trailing zeros are significant Trailing zeros are significant 300 – 3 sig figs0.003- 1sig fig 300 – 3 sig figs0.003- 1sig fig 30.0 – 3 sig figs 30.0 – 3 sig figs 010010 -? Sig figs 010010 -? Sig figs In scientific notation the integers preceding the ∙10 x are significant. In scientific notation the integers preceding the ∙10 x are significant. 1.3∙10 6 -2 sig figs 1.3∙10 6 -2 sig figs Conversion factors are assumed to have an infinite number of sig figs. Conversion factors are assumed to have an infinite number of sig figs.

13. Mathematical operations with Sig. Figs When multiplying or dividing keep only the lowest number of significant figures When multiplying or dividing keep only the lowest number of significant figures When adding or subtracting keep only the lowest number of decimal places When adding or subtracting keep only the lowest number of decimal places 32*2 = 6∙10 1 32*2.0=64 32*2 = 6∙10 1 32*2.0=64 1.3+2.54=3.81 - 0.54 = 0 1.3+2.54=3.81 - 0.54 = 0 0.5*300 = ?100.2+18.65 = ? 0.5*300 = ?100.2+18.65 = ?

14. Dimensional Analysis A check of the possible validity of a formula by comparing the units on each side of the equation. A check of the possible validity of a formula by comparing the units on each side of the equation. QuantityVariable symbolDimension Length Distance Position Displacement l d x,y,r Δx, Δy, Δr L MassmM TimetT VelocityvL/T AccelerationaL/T 2

15. We notate the dimensionality of a quantity as follows. We notate the dimensionality of a quantity as follows. [x] = L where x is a position When adding quantities each term must have the same dimensionality When adding quantities each term must have the same dimensionality If A=B+C then [A]=[B]=[C] The dimensionality of a product is given as follows The dimensionality of a product is given as follows[AB]=[A][B] The dimensionality of a dimensionless constant, κ, is 1. [κ]=1 ex: ½,  The dimensionality of a dimensionless constant, κ, is 1. [κ]=1 ex: ½, 

16. Dimensional Analysis Ex: Is the following equation dimensionally consistent? Is the following equation dimensionally consistent? x=x o + v∙t +1/2 a∙t 2 x=x o + v∙t +1/2 a∙t 2 [x] = L, [v] = L/T, [t]=T, [1/2] =1, [a]=L/T 2 [x] = L, [v] = L/T, [t]=T, [1/2] =1, [a]=L/T 2 L = L + (L/T)T + (L/ T 2 )T 2 L = L + L + L

17. Example from Conceptual Ex.

18. Round Off Errors Round off errors are deviations of a solution (usually but not always small) from the actual solution due to rounding intermediate calculations in route to the final solution. Round off errors are deviations of a solution (usually but not always small) from the actual solution due to rounding intermediate calculations in route to the final solution. If possible reduce all problems to an algebraic solution then calculate a numeric answer. If possible reduce all problems to an algebraic solution then calculate a numeric answer.