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Modern Physics

Modern Physics

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Modern Physics

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  1. Modern Physics

  2. Photon Energy • Scalar • photon - bundle of light • use Planck’s constant • directly related to frequency • inversely related to wavelength

  3. Einstein’s demo of quantized light the ‘reverse light bulb’ Proof that light is a particle contributes to photon collision theory Photoelectric Effect

  4. Bohr Model • electrons fit in exact energy levels • quantized energy • release photon as electron falls • absorb photon (or other energy) as electron jumps up

  5. Hydrogen Energy Levels • know the Balmer series is visible • use energy difference to know posible jumps • same for mercury energy levels

  6. Energy equivalent of mass • mass can change to energy • use c= 3.00 x 108 m/s • kg relates to J • amu relates to MeV

  7. Universal Mass Units • Don’t use E=mc2 for universal mass units • Just use the conversion factor given

  8. Classification of Matter • there are subparticle beyond the protons and neutrons...but they don’t stand alone • p+ and n0 are baryons • e- are leptons • the sum of quarks is always an integer

  9. Particles of the Standard Model • the first column defines protons neutrons and electrons • antiparticles have a bar above the symbol • antiparticles have opposite magnetic moment and charge

  10. Physics Regents Review 2009 Welcome to the Physics Regents Exams St. Mary's Physics Online

  11. MATH AND METHODS

  12. Math Resources – Bring pens, pencils, calculator, protractor

  13. PRACTICE • http://www.greatneck.k12.ny.us/GNPS/SHS/dept/science/wells/regentswkbk.pdf

  14. Know Scalars and Vectors • SCALARS • Speed • Distance • Mass • Time • Energy • Power • VECTORS • Velocity • Displacement • Acceleration • Force (and weight) • Momentum • Field

  15. What is the distance?What is the displacement?

  16. Resultant of any two vectors fall between max at (sum) and min (difference)

  17. Speed and Velocity • speed - scalar • velocity - vector • this is the slope of the distance v. time graph • memorize that average can also be final plus initial divided by two

  18. Identify the variables in each problem statement

  19. At rest means v=0m/s

  20. Acceleration • Acceleration is always a vector • slope of velocity v. time graph • 9.81m/s2 for freefall

  21. The only acceleration of a projectile is 9.8m/s2 vertically down

  22. Final Speed • same as acceleration equation • we only calculate constant uniform acceleration problems

  23. The distance equation • most common equation for freefall and projectiles • Vi is zero for freefall • a is 9.81m/s2 for y direction near the earth

  24. The no time motion equation! • use when time is not given • usually Vi or Vf is zero

  25. Mass v Weight • Inertia is mass • Weight always acts down • Mass does not depend upon position, weight does

  26. Slope of displacement v. time is speedSlope of speed v. time is acceleration

  27. Resolving vectors into components projectile speed V can become Vx and Vy Force at an angle can become Fx and Fy

  28. Time connects vertical motion to horizontal motion

  29. What is Force?

  30. F=ma....Newton’s Second Law • The most important equation in mechanics! • Fnet is the sum of all the forces ... • this equation can be applied in any one dimension

  31. Frictional Force • Vector • Normal force is weight if on a horizontal surface • Always opposes motion or intended motion • does not depend on surface area

  32. Friction does not conserve mechanical energy- it transforms energy to heat

  33. Friction opposes relative motion between the objects in contact (opposes the direction of velocity)

  34. INCLINED PLANEForce parallel is WsinqForce perpendicular is Wcosq

  35. Problem • A 1200-kilogram car moving at 12 meters per second collides with a 2300-kilogram car • that is waiting at rest at a traffic light. After the collision, the cars lock together and slide. • Eventually, the combined cars are brought to rest by a force of kinetic friction as the • rubber tires slide across the dry, level, asphalt road surface. • 59 Calculate the speed of the locked-together cars immediately after the collision. [Show all work, including • the equation and substitution with units.] [2]

  36. Coefficient of Friction • no units • depends on the materials in contact • unaffected by area • kinetic is moving • static is resisting motion

  37. Universal Gravitation • Vector ....newtons • depends on each mass • decreases as distance (r) increases

  38. Universal gravitation is an inverse square relationship

  39. The sun is one focus of the solar system ellipse Satellite speed is fastest closer to the body it travels aroundGeosynchronous orbit period is 1 day ORBITS!

  40. Gravitaional Field • vector...newtons • the accelerational field is the same as acc. due to gravity • 9.81m/s2 at the surface of the earth • it is a uniform field • neglect air resistance

  41. Gravity Goes......??? • 9.8m/s2 • neglect air resistance