1 / 32

Homework : (55 points) 92 review problems

What is the difference between longitudinal and transverse waves? Give an example of each How much power is dissipated by the circuit to the right. ( Eq : P = I 2 R = I V) What is the current through the 2-ohm resistor below? . Homework : (55 points) 92 review problems. Types of Waves.

lea
Download Presentation

Homework : (55 points) 92 review problems

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. What is the difference between longitudinal and transverse waves? Give an example of each • How much power is dissipated by the circuit to the right. (Eq: P = I2 R = I V) • What is the current through the 2-ohm resistor below? Homework: (55 points) 92 review problems

  2. Types of Waves Transverse wave: medium vibrates at right angles to the direction the energy moves λ Compression wave: (longitudinal wave) medium vibrates in the same direction as the direction the energy moves

  3. http://www.youtube.com/watch?v=Rbuhdo0AZDU Types of Waves:

  4. Music

  5. Electromagnetic Waves • Mechanical waves require a mediumin order to travel. • examples: • electromagnetic waves do not require a medium water, earthquakes, and sound

  6. 2. How much power is dissipated by the circuit below? Given Equation 1 Equation 2 R = 200 Ω V = I R P = I V V = 100 V

  7. 3. What is the current through the 2-ohm resistor below?   Equation V = I R Given R1 = 2 Ω V = 10 V Parallel circuit: Voltage is equal at both resistors

  8. How much power is dissipated by the circuit to the right. (Eq: P = I2 R = I V) • What is the current through the 2-ohm resistor below? Homework: (55 points) Finish Review Problems (6) Reading Log 501-503

  9. Quiz! • Clear your desks! • Grab a pencil! • Get ready!... Get set!…. GO!

  10. Momentum

  11. Momentum • What is the difference between kicking a: • stationary ball? • ball travelling towards you at 30 mph? • Newton solution: moving inertia

  12. Momentum vector (direction is important) • Units: kgm / s

  13. Momentum • Let’s try it: • momentum of a 50kg person walking at 2 m/s • momentum of a speeding bullet which would you stand in front of?

  14. Danger • Why does bullet have more effect? • energy of a walking person • energy of a speeding bullet energy!

  15. Physics of “Soft” • Falling can have different results • Hard landing: • Soft landing: able to walk away • What’s the difference? Broken bones, pain… Phew! How you change the momentum

  16. Changing Momentum • Let’s connect the force to momentum: • Substitute with impulse • Impulse is the change in momentum

  17. Changing Momentum • Physics of “soft” refers to how momentum is reduced • For example: two 50kg kids jump off a 12 ft (~4 m) building. • Kid 1 lands with straight legs • Kid 2 tucks and rolls when landing

  18. Changing Momentum • Which kid hits the ground faster? • both land with same speed: • At the bottom, they both have the same momentum:

  19. Changing Momentum • In order to stop, their impulse will have to be: • Kid 1 has a really short landing, 0.05 s • Kid 2 makes the landing last longer, 1.0 s • We can use the impulse to find the force each kid feels

  20. Changing Momentum • Kid 1 • Kid 2 • A pound is about 4Newtons, so • Kid 1 feels about 2,000lbs • Kid 2 feels about 100lbs (broken bones) (piggy back ride)

  21. Changing Momentum • Kid 1 • Ft • Kid 2 • Ft • You can always make a soft change if the impulse time is long enough

  22. Time to Practice Go to pg. 506

  23. Physics of Catastrophe • Catastrophic event: • collisions • explosions • In order to know the velocity after, you need to know the momentum before

  24. Conservation of Momentum • Main reason Newton used • It is conserved! • So, all the total momentum before something explodes • Is thesame after it explodes!

  25. Conservation of Momentum • But initially it was not moving! • Since momentum is a vector: • All of the xvectors add to zero • All of the y vectors add to zero

  26. Conservation of Momentum • Same for crashes • All the momentum before the crash • Is the same after the crash • Let’s try one…

  27. Example A 65 kg swimmer runs with a horizontal velocity of 5.6 m/s off a dock He jumps into a 15 kg rubber raft that is drifting towards him with a velocity of 1.0 m/s What is the velocity of the swimmer and raft after the impact? (assume no friction or resistance due to air or water)

  28. Example • A 65 kg swimmer runs with a horizontal velocity of 5.6 m/s off a dock • He jumps into a 15 kg rubber raft that is drifting towards him with a velocity of 1.0 m/s • What is the velocity of the swimmer and raft after the impact? • Start by drawing a diagram for before and after vf vf or

  29. Diagram • Before: • After: notice the subscripts How will v1f compare to v2f?

  30. Set up conservation equation only one vf which direction is vf?

  31. Try this out! Answer questions 89-92 on your review sheet Turn it in on a separate piece of paper by the end of class (Disclaimer: These questions do not count as part of your 42 problems)

More Related