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Physics

Physics. Einstein, atomic bombs, spacecraft, math Baseballs, roller coasters, toasters, rainbows, cats The study of the physical world , the most fundamental of the sciences. The behavior and structure of matter. Hypothesis - a conjecture to be used as a basis for further investigation

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Physics

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  1. Physics • Einstein, atomic bombs, spacecraft, math • Baseballs, roller coasters, toasters, rainbows, cats • The study of the physical world, the most fundamental of the sciences. • The behavior and structure of matter.

  2. Hypothesis- a conjecture to be used as a basis for further investigation • Theory- a synthesis of a large body of information that encompasses well-tested and verified hypotheses • Fact- close agreement by many competent observers of the same phenomenon. • Law- a concise statement about how nature behaves

  3. The metric system The System Internationale, SI Standards of length, time, and mass Length: meter, m Time: second, s Mass: kilogram, kg Derived units: a combination of fundamental units, such as meter per second, m/s

  4. Measurement uncertainties Precision: the degree of exactness, is limited by the divisions on the scale Accuracy: how well the measure agrees with an accepted standard.

  5. Good measurements Parallax, the apparent shift in the position of an object when it is viewed from different angles.

  6. Scientific Notation and Rounding 356,000,000,000 3.56 x 1011 0.0000000003 3 x 10-10 238567489 2.38 x 108 When moving the decimal point, the exponent changes: Left – Larger Right- Reduced 53.456782 53.46

  7. It’s 1500 miles to Fresno, California • ….EXACTLY 1500 miles??? • Which numerals are significantly important in the measurement of a quantity?

  8. The rules for Significant Digits • All non-zero digits are significant. • All zeros are significant unless the zeros are at the beginning of a numeral. Examples: 238 23.0 2370 0.48 200250 0.00562 0.24020 10000 ? Put in scientific notation!

  9. Graphing Data Independent axis: the x-axis- horizontal Dependent axis: the y-axis- vertical The y values depend on the x values

  10. Graphing Data Linear relationship, y = mx + b Inverse relationship y = b/x, b = rational number Quadratic relationship y = bx2

  11. Position- the location of an object relative to a reference point. We often use the letter x to represent position. (“x marks the spot” Sometimes we also use “d”, when position is some measured distance, d, from a reference point. Reference point-the point from which measurements are made. Linear Motion

  12. Distance- how far something moves. Displacement– how far something moves in a given direction. (It’s only concerned about where you started and where you stopped, not what you did in between.) Negative?? For example: if you take a trip all the way around the world and end up right back where you started, you traveled a great distance, but your displacement was zero!

  13. Rate- a quantity divided by time- how much something is changing in a certain amount of time • Speed- the rate at which position changes- • “how fast?” Example: 60 miles per hour- the position of a car will change 60 miles in one hour. We will use m/s most often.

  14. Average speed = total distance covered ÷ time interval • Instantaneous speed- the speed at any instant

  15. D - “delta”- a symbol that means “the change in” the change in position, D x Change in time, D t Change in velocity, D v The change in a value is the difference between the final value and the original value- “final minus original” • velocity = final velocity – original velocity Example: a car was moving at 18 m/s and then sped up to 22 m/s. What was D v ? D v = 22 m/s - 18 m/s = 4 m/s

  16. Speed and Velocity In physics, speed and velocity are not the same! Speed is “how fast”, Velocity is “how fast and in what direction”. Example: 10 m/s is a speed, 10 m/s north is a velocity

  17. “uniform” means “constant, unchanging” At a uniform speed, the distance traveled is given by Distance = speed x time At uniform velocity, the displacement is given by Displacement = velocity x timed = vt

  18. Examples • How far will you go while traveling at 23 m/s for 12 seconds? d = vt = 23 m/s x 12 s = 276 m

  19. How long will it take to travel a distance of 240 km traveling at 12 m/s? Convert 240 km to meters first! 240 km x = 240000 m Rearrange the equation d = vt to solve for t t = d ÷ v = 240000 m ÷ 12 m/s = 20000 s

  20. How far, in meters, will you go while traveling at 70 km/h for 18 seconds? • Convert to the 70 km/h to m/s first, then calculate the distance. 70 = 19.4 m/s d = vt = 19.4 m/s x 18 s = 349 m

  21. Remember, displacement = Dposition = Dx So…. xf – xo = vt There are times when you know the original position but not the final or vice versa.

  22. Graphing Motion The velocity of an object can be found by determining the SLOPE on a position-time graph.

  23. Velocity (m/s) What is the velocity? At 1 s? At 4 s? At 7 s? At 12 s? At 17 s? What is the acceleration? From 0 – 2s? From 2 – 6 s? From 9 – 11 s? From 11-14 s? From 14 – 22 s? 8 6 4 2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Time (s) -2 -4 -6 -8 Velocity-Time Graphs

  24. Velocity (m/s) What is the velocity? At 1 s? 6m/s At 4 s? 3m/s At 7 s? 0 At 12 s? -8m/s At 17 s? -4m/s What is the acceleration? From 0 – 2s? 0 From 2 – 6 s? -1.5 m/s2 From 9 – 11 s? -4m/s2 From 11-14 s? 0 From 14 – 22 s? +1.4m/s2 8 6 4 2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Time (s) -2 -4 -6 -8 Velocity-Time Graphs What about the displacement?

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