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Dr. Persin and Lnk2Lrn present FCAT Physics

Dr. Persin and Lnk2Lrn.com present FCAT Physics. Physics Topics Motion Measuring Matter Work, Power, Machines Newton’s Laws Waves Momentum Pressure. Acceleration of a car. Acceleration is the rate of change in the speed of an object. Acceleration vs. Speed.

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Dr. Persin and Lnk2Lrn present FCAT Physics

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  1. Dr. Persin and Lnk2Lrn.compresentFCAT Physics

  2. Physics Topics Motion Measuring Matter Work, Power, Machines Newton’s Laws Waves Momentum Pressure

  3. Acceleration of a car Acceleration is the rate of change in the speed of an object.

  4. Acceleration vs. Speed • Positive acceleration and positive speed

  5. Acceleration vs. Speed • Negative acceleration and positive speed

  6. Acceleration Change in speed (m/sec) Acceleration (m/sec2) = Change in time (sec)

  7. Calculate Acceleration • A student conducts an • acceleration experiment by coasting a bicycle down a steep hill. • The student records the speed of the bicycle every second for five seconds. • Calculate the acceleration of the bicycle.

  8. Acceleration and Speed • Constant acceleration is different from constant speed. • Motion with zero acceleration appears as a straight horizontal line on a speed versus time graph. zero acceleration constant speed

  9. Acceleration and Speed • Constant acceleration is sometimes called uniform acceleration. • A ball rolling down a straight ramp has constant acceleration. constant acceleration increasing speed

  10. Acceleration and Speed • An object can have acceleration, but no speed. • Consider a ball rolling up a ramp. • As the ball slows down, eventually its speed becomes zero. constant negative acceleration decreasing speed

  11. Measuring Matter MASS, VOLUME, & DENSITY

  12. MASS… • Definition: Amount of matter in an object • Units: kg or g • Mass is different from weight because…Weight depends on pull of gravity

  13. VOLUME… • Definition: How much space an object takes up • Regular shaped object (box) then V= L x W x H (cm3 or m3) • Liquids - to find volume…use graduated cylinder (mL or L) • Use graduated cylinder for odd shaped solid objects (cm3 or m3)

  14. How to measure the volume of an odd shaped solid • Obtain a clean graduated cylinder. • Fill the graduated cylinder with enough water to cover object. Record the volume • Carefully place the object into the water filled graduated cylinder. • Record the new water level. • The volume of the object is the Vfinal – Vinitial

  15. DENSITY…. • Density is the measurement of the mass of an object per unit volume of that object. • Formula: D (density) = m (mass) V(volume)

  16. Example Density Calculation: • A rock has a mass of 25.7 grams and a volume of 3.56 cm3. Find the density. • 1st write: D = mass volume • 2nd: Substitute in the measurements D = 25.6 g 3.56 cm3 • 3rd: Calculate following sig fig rules. Density = 7.19 g/ cm3

  17. PRACTICE…. • Calculate the density of a marble that has a mass of 13.6 grams and a volume of 6.1 cm3. • D = m/V = 13.6 g / 6.1 cm3 • D = m/V = 2.2 g / cm3

  18. Principle 1 • If you pack more mass into the same volume, it is more dense. • Example: packing wet sand into a bucket

  19. Principle 2 • If you pack the SAME mass into a SMALLER volume, it is MORE dense • Example: a trash compactor.

  20. Principle 3 • Just because something has more mass DOES NOT mean it is more DENSE.

  21. Work, Power and Machines

  22. Force 40 N Force acting through a distance Distance 10 m Work W = F * d = 40 N * 10 m = 400 Joules

  23. Work • Force must be in same direction as distance Force Distance

  24. Even though machines make work easier, Work Input is always greater than Work Output due to Friction % Efficiency = Work Output / Work Input *100 Work Input Work Output Feffort*distance Fresistance*distance 10N*5m = 50J 20N*2m = 40J

  25. Even though machines make work easier, Work Input is always greater than Work Output due to Friction % Efficiency = (40 J / 50 J) = 0.8 Work Input Work Output Feffort*distance Fresistance*distance 10N*5m = 50J 20N*2m = 40J

  26. Newton’s Laws • I. Law of Inertia • II. F = ma • III. Action / Reaction                                                  <>

  27. Aforce is… a push or a pull. Friction, Drag, Gravity, and Weight are forces…

  28. Law I: Inertia vs. Mass Bigger masses have more… Inertia Smaller masses have less inertia. But inertia does not equal mass.

  29. Newton’s 2nd Law: F = ma Force equals mass x acceleration

  30. F = ma mass = 10 kg acceleration = 2 m/s 2 Find the Force. F = 10 kg x 2 m/s = 20 N 2

  31. Newton’s 3rd Law: Action Reaction

  32. You exert force on the weights and… The weights exert the same force on you.

  33. Water is pushed back and… the boat is pushed forward.

  34. Physics FCAT Dr. Persin Making Waves

  35. Waves What are waves?

  36. What is a wave? a wave is a disturbance that travels away from a source.

  37. sound waves visible light waves radio waves microwaves water waves sine waves telephone chord waves stadium waves earthquake waves waves on a string slinky waves Waves are everywhere in nature, not just on the ocean.

  38. Why study waves? • Waves transfer energy with transferring matter. • Lets do a Stadium Wave!

  39. Wave • A wave transfers energy from place to place. • What carries waves? • A medium, a medium is the material through which a wave travels. • A medium can be a gas, liquid, or solid.

  40. What causes waves? • Waves are created when a source of energy causes a medium to vibrate. • A vibration is a repeated back and forth or up and down motion.

  41. The Wave Equation v = fl v = velocity f =frequency l = wavelength

  42. Wave Equation Units v = velocity, m/s f = frequency, Hertz (Hz) λ= wavelength, m λ is the Greek letter “lambda”

  43. PRACTICE…. • Calculate the velocity of a wave with a frequency of 250 Hz and a wavelength of 3 m. • v = fl= 250 Hz  3 m • v = 750 m/s

  44. Introduction to MomentumFCAT Physics Part II

  45. Momentum = mass * velocity What is momentum? All objects have mass. So if an object is moving, then it has momentum. It is mass in motion. Equation: p = m V

  46. a little math … Determine the momentum of a ... a. 60 kg body moving at 9 m/s. b. 1000 kg car moving at 20 m/s. c. 40 kg freshman moving at 2 m/s Answers: a. 540 kg m/s b. 20,000 kg m/s c. 80 kg m/s

  47. Conceptual Check:

  48. Conceptual Check: Which has a greater momentum, a skateboard moving at 3 m/s or a stationary ten-wheeler truck ? Explain your answer. When can a ball have the same momentum as an airplane parked on a runway? Explain your answer.

  49. Momentum Rocket = Momentum Exhaust A 20 kg rocket zooms upward at 5 meter/second. At the same exact time, 10 kg of water shoots downward. How fast does the water shoot out?

  50. Momentum Transfers in Collisions Here is an example.

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