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## Regent Physics PowerPoint Presentation

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**Physics Units**• I. Physics Skills • II. Mechanics • III. Energy • IV. Electricity and Magnetism • V. Waves • VI. Modern Physics**I. Physics Skills**• A. Scientific Notation • B. Graphing • C. Significant Figures • D. Units • E. Prefixes • F. Estimation**A. Scientific Notation**• Use for very large or very small numbers • Write number with one digit to the left of the decimal followed by an exponent (1.5 x 105) • Examples: 2.1 x 103 represents 2100 and 3.6 x 10-4 represents 0.00036**Scientific Notation Problems**• 1. Write 365,000,000 in scientific notation • 2. Write 0.000087 in scientific notation**Answers**• 1.) 3.65 x 108 • 2.) 8.7 x 10-5**B. Graphing**• Use graphs to make a “picture” of scientific data • “independent variable”, the one you change in your experiment is graphed on the “x” axis and listed first in a table • “dependent variable”, the one changed by your experiment is graphed on the “y” axis and listed second in a table**Best fit “line” or “curve” is drawn once points are**plotted. Does not have to go through all points. Just gives you the “trend” of the points • The “slope” of the line is given as the change in the “y” value divided by the change in the “x” value**Types of Graphs**• 1. Direct Relationship means an increase/decrease in one variable causes an increase/decrease in the other • Example below**2. Inverse(indirect) relationship means that an increase in**one variable causes a decrease in the other variable and vice versa • Examples**3. Constant proportion means that a change in one variable**doesn’t affect the other variable Example;**4. If either variable is squared(whether the relationship is**direct or indirect), the graph will curve more steeply.**C. Significant figures**• Uncertainty in measurements is expressed by using significant figures • The more accurate or precise a measurement is, the more digits will be significant**Significant Figure Rules**• 1. Zeros that appear before a nonzero digit are not significant (examples: 0.002 has 1 significant figure and 0.13 has 2 significant figures) • 2. Zeros that appear between nonzero digits are significant (examples: 1002 has 4 significant figures and 0.405 has 3 significant figures)**Significant figures rules(cont.)**• 3. zeros that appear after a nonzero digit are significant only if they are followed by a decimal point (20. has 2 sig figs) or if they appear to the right of the decimal point (35.0 has 3 sig figs)**Sig Fig problems**• 1. How many significant figures does 0.050900 contain? • 2. How many significant figures does 4800 contain?**Answers**• 1. 5 sig figs • 2. 2 sig figs**D. Units**• 1. Fundamental units are units that can’t be broken down • 2. Derived units are made up of other units and then renamed • 3. SI units are standardized units used by scientists worldwide**Fundamental Units**• Meter (m)– length, distance, displacement, height, radius, elongation or compression of a spring, amplitude, wavelength • Kilogram (kg)– mass • Second (s)– time, period • Ampere (A)– electric current • Degree (o)– angle**Derived Units**• Meter per second (m/s)– speed, velocity • Meter per second squared (m/s2)– acceleration • Newton (N)– force • Kilogram times meter per second (kg.m/s)– momentum • Newton times second (N.s)-- impulse**Derived Units (cont.)**• Joule (J)– work, all types of energy • Watt (W)– power • Coulomb (C)– electric charge • Newton per Coulomb (N/C)– electric field strength (intensity) • Volt (V)- potential difference (voltage) • Electronvolt (eV)– energy (small amounts)**Derived Units (cont.)**• Ohm (Ω)– resistance • Ohm times meter (Ω.m)– resistivity • Weber (Wb)– number of magnetic field (flux) lines • Tesla (T)– magnetic field (flux) density • Hertz (Hz)-- frequency**E. Prefixes**• Adding prefixes to base units makes them smaller or larger by powers of ten • The prefixes used in Regents Physics are tera, giga, mega, kilo, deci, centi, milli, micro, nano and pico**Prefix Examples**• A terameter is 1012 meters, so… 4 Tm would be 4 000 000 000 000 meters • A gigagram is 109 grams, so… 9 Gg would be 9 000 000 000 grams • A megawatt is 106 watts, so… 100 MW would be 100 000 000 watts • A kilometer is 103 meters, so… 45 km would be 45 000 meters**Prefix examples (cont.)**• A decigram is 10-1 gram, so… 15 dg would be 1.5 grams • A centiwatt is 10-2 watt, so… 2 dW would be 0.02 Watt • A millisecond is 10-3 second, so… 42 ms would be 0.042 second**Prefix examples (cont.)**• A microvolt is 10-6 volt, so… 8 µV would be 0.000 008 volt • A nanojoule is 10-9 joule, so… 530 nJ would be 0.000 000 530 joule • A picometer is 10-12 meter, so… 677 pm would be 0.000 000 000 677 meter**Prefix Problems**• 1.) 16 terameters would be how many meters? • 2.) 2500 milligrams would be how many grams? • 3.) 1596 volts would be how many gigavolts? • 4.) 687 amperes would be how many nanoamperes?**Answers**• 1.) 16 000 000 000 000 meters • 2.) 2.500 grams • 3.) 1596 000 000 000 gigavolts • 4.) 0.000 000 687 amperes**F. Estimation**• You can estimate an answer to a problem by rounding the known information • You also should have an idea of how large common units are**Estimation (cont.)**• 2 cans of Progresso soup are just about the mass of 1 kilogram • 1 medium apple weighs 1 newton • The length of an average Physics student’s leg is 1 meter**Estimation Problems**• 1.) Which object weighs approximately one newton? Dime, paper clip, student, golf ball • 2.) How high is an average doorknob from the floor? 101m, 100m, 101m, 10-2m**Answers**• 1.) golf ball • 2.) 100m**II. Mechanics**• A. Kinematics; vectors, velocity, acceleration • B. Kinematics; freefall • C. Statics • D. Dynamics • E. 2-dimensional motion • F. Uniform Circular motion • G. Mass, Weight, Gravity • H. Friction • I. Momentum and Impulse**Kinematics; vectors, velocity, acceleration**• In physics, quantities can be vector or scalar • VECTOR quantities have a magnitude (a number), a unit and a direction • Example; 22m(south)**SCALAR quantities only have a magnitude and a unit**• Example; 22m**VECTOR quantities; displacement, velocity, acceleration,**force, weight, momentum, impulse, electric field strength • SCALAR quantities; distance, mass, time, speed, work(energy), power**Distance vs. Displacement**• Distance is the entire pathway an object travels • Displacement is the “shortest” pathway from the beginning to the end**Distance/Displacement Problems**• 1.) A student walks 12m due north and then 5m due east. What is the student’s resultant displacement? Distance? • 2.) A student walks 50m due north and then walks 30m due south. What is the student’s resultant displacement? Distance?**Answers**• 1.) 13m (NE) for displacement 17 m for distance • 2.) 20m (N) for displacement 80 m for distance**Speed vs. Velocity**• Speed is the distance an object moves in a unit of time • Velocity is the displacement of an object in a unit of time**Speed/Velocity Problems**• 1.) A boy is coasting down a hill on a skateboard. At 1.0s he is traveling at 4.0m/s and at 4.0s he is traveling at 10.0m/s. What distance did he travel during that time period? (In all problems given in Regents Physics, assume acceleration is constant)**Answers**• 1.) You must first find the boy’s average speed/velocity before you are able to find the distance**Acceleration**• The time rate change of velocity is acceleration (how much you speed up or slow down in a unit of time) • We will only be dealing with constant (uniform) acceleration**Constant Acceleration Problems**• 1.) A car initially travels at 20m/s on a straight, horizontal road. The driver applies the brakes, causing the car to slow down at a constant rate of 2m/s2 until it comes to a stop. What was the car’s stopping distance? (Use two different methods to solve the problem)**Answers**• First Method vi=20m/s vf=0m/s a=2m/s2 Use vf2=vi2+2ad to find “d” d=100m