St. Augustine Preparatory School Physics Chapter 1 St. Augustine Preparatory School

The Scientific Method Physics follows the scientific method Make observations and collect data - This will allow you to formulate a question 2) Create and test a hypothesis through controlled experimentation 3) Interpret results and revise hypothesis if necessary 4) State conclusions in a form that can be evaluated by others

Using Models Physics can often be very complex, so simplified models can be used System – the interacting components considered to be necessary for the purpose of the study

Example: Improving the fuel efficiency of a vehicle. Things that could potentially matter:

To run a legitimate and effective study, we cannot change all of these variables at once. We must also run a “control” group that has only changed one variable. The best physics models can make predictions in new situations

If we drop a roll of tape and a piece of paper at the same time, which one is going to hit the ground first? What about in a vacuum? (youtube video) What can we conclude from both of these trials?

SI Units In 1960, an international committee decided on a system of standards and units, known as SI units (Systeme International d’Unites). We have 7 base units in SI: meter 2) kilogram 3) second 4) ampere 5) candela 6) kelvin and 7) mole

Random Facts: Unit Original Standard Current Standard Meter (length) 1/10 000 000th the distance from the equator to the North Pole The distance travelled by light in a vacuum in 3.33564095 x10-9 s Kilogram (mass) Mass of 0.001 cubic meters of water The mass of a specific platinum-iridium alloy cylinder Second (time) (1/60)(1/60)(1/24) = 0.000 011 574 average solar days 9 192 631 770 times the period of a radio wave emitted from cesium-133 atom

These 7 cannot explain everything though… These units have been combined to create what we call “derived units” Example: Velocity is measured in m/s (meters per second) However, force is measured in N (Newton’s)

Prefixes for units You are required to know the following prefixes for units: Pico (p): 10-12 g) kilo(k): 103 Nano(n): 10-9 h) mega(M): 106 Micro(μ): 10-6 i) giga(G): 109 Milli(m): 10-3 j) tetra(T): 1012 Centi(c): 10-2 deci(d): 10-1

Conversions Example: Convert 162000g to Mg Example: Convert 1312km to meters

Practice conversions 10 kilograms in megagrams 0.00342 kilometers in centimeters 132.5 cm in decimeters 132 millimeters to micrometers 5) 262,523 micrometers in meters 6) 2329 picograms to milligrams

Significant Figures Significant figures (also called significant digits) are important as they indicate the precision of a measurement Page 18 in your textbook has the rules for determining the amount of significant figures in a number

Practice 1.0303 m h) 1000 kg 2.50 kg i) 6.723 m 0.00032 s j) 4.200 J 3.0x102 mm 45 s 40 s 2.2830 km

Rules for addition and subtraction When adding and subtracting numbers, the final answer will have the same number of decimal places as the number used in the addition/subtraction that had the least number of decimal places. Examples: 121.03 + 5.8 = 125 – 5.5 =

Rules for multiplication and division When multiplying and dividing, the final answer must have the same number of significant figures as the number used that had the least number of significant digits. Examples: 24.0 x 1.5 = 36.00/2.00 =

Practice 97.3 + 5.85 = 122.3 – 0.52 = (124.2)(2.1) = (2x102)(1.232) = 24.56 / 2.3213 = 2.02x106 + 1.3x105 = 1.000 + 2.01 + 3.523 + 2.6 = (1.20)(2.212)(0.0035) =