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Physics

Physics . Topics of Physics. Mechanics – Motion and its causes Thermodynamics – Heat and Temperature Waves – Repetitive Motion Optics – Light Electromagnetism – Electricity, Magnetism and Light Relativity – Moving Particles Quantum Mechanics – Submicroscopic Particles. Models.

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Physics

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  1. Physics

  2. Topics of Physics • Mechanics – Motion and its causes • Thermodynamics – Heat and Temperature • Waves – Repetitive Motion • Optics – Light • Electromagnetism – Electricity, Magnetism and Light • Relativity – Moving Particles • Quantum Mechanics – Submicroscopic Particles

  3. Models A replica designed to show the structure or workings of an object, system, or concept. A system consists of a single object and the items that immediately affect it. Help build hypothesis and guide experimental design

  4. Units All measurements in physics MUST have a unit. 1 m tells me an object is 1 meter in length. 1 without a unit tells me nothing! Units MUST agree! Multiplying 1 cm x 1 m is not possible! 1 cm = 100 m therefore 1 cm x 1m = 100 m x 1 m = 100 m

  5. Metric Conversions Base-10 system Each prefix is 10 times larger or smaller than the next king henry died by drinking chocolate milk

  6. Scientific Notation Simple way to write really large or really small numbers Large numbers have a positive exponent (numbers greater than 1) Small numbers have a negative exponent (numbers between 0 and 1)

  7. Equations Indicate Relationships Greek letter delta (change in) Always rearrange the equation BEFORE plugging in numbers!

  8. Equations Solve the following equation for acceleration.

  9. Dimensional Analysis • Units cancel • If you don’t have the units you want when you are done then you did something wrong.

  10. Dimensional Analysis A billionaire offers to give you $5 billion if you will count out the amount in $1 bills or a lump sum of $5000. Which offer should you accept? (Assume that you can count at an average rate of one bill per second, and be sure to allow for the fact that you need about 10 hours a day for eating and sleeping.)

  11. Dimensional Analysis Take the $5000!!! It would take you 272 years to count out the $5 billion!

  12. Graphs Summarize Data Indicate Relationships Make Inferences and Predictions

  13. Graphs • Determine the slope of the line in each of the following graphs. 1. 2.

  14. Graphs 1. 2. Slope = 1.5 Slope = -1.5

  15. Graphs slope y = mx + b y-intercept

  16. Graphs Identify the graph that matches each of the following stories: I had just left home when I realized I had forgotten my books so I went back to pick them up. Things went fine until I had a flat tire. I started out calmly, but sped up when I realized I was going to be late.

  17. Graphs Answer these questions about the graph on the right: How many total miles did the car travel? What was the average speed of the car for the trip? Describe the motion of the car between hours 5 and 12? What direction is represented by line CD? How many miles were traveled in the first two hours of the trip? Which line represents the fastest speed?

  18. Angles Things do not always move in a straight line Understanding how to measure and use basic angles makes things easier.

  19. Angles

  20. Angles If the baseline is 100 m and the angle at B is 60°, determine the distance from A to the tree.

  21. Angles opposite Tan B = adjacent distance to object Tan B = baseline (Tan B)(baseline) = distance to object (Tan 60)(100 m) = distance to object distance to object (1.73)(100 m) = 173 m = distance to object

  22. Review • Models help us to understand how things work. (Leads to hypotheses and experimental design) • Units are essential. No unit = No Credit! • Equations indicate relationships. (Always solve for the variable before plugging in the numbers) • Dimensional analysis can weed out invalid equations. • Graphs allow us to make inferences and predictions. • Understanding angles makes it easier to solve problems

  23. Practice Problem The radius of the planet Saturn is 5.85 x 107 m, and its mass is 5.68 x 1026 kg. • Find the density of Saturn (its mass divided by its volume) in grams per cubic centimeter. (The volume of a sphere is given by ) Correct Answer – 0.677 g/cm3 • Find the surface area of Saturn in square meters. (The surface area of a sphere is given by 4) Correct Answer – 4.30 x 1016 m2

  24. Practice Problem Assuming biological substances are 90 percent water and the density of water is 1.0 x 103 kg/m3, estimate the masses (density multiplied by volume) of the following: • A spherical cell with a diameter of 1.0 µm (The volume of a sphere is given by ) Correct Answer – 5x 10-16 kg • A fly, which can be approximated by a cylinder 4.0 mm long and 2.0 mm in diameter. (The volume of a cylinder is given by l) Correct Answer – 1 x 10-5kg

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