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Bellringer – 2 mins to hand in

Bellringer – 2 mins to hand in. A 67kg ice skater is moving at a constant velocity of 10m/s when he collides and holds onto a 50kg ice skater who was originally at rest. What is their momentum after the collision?. DO WORK. STOP. Objectives.

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Bellringer – 2 mins to hand in

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  1. Bellringer – 2 mins to hand in • A 67kg ice skater is moving at a constant velocity of 10m/s when he collides and holds onto a 50kg ice skater who was originally at rest. What is their momentum after the collision? DO WORK STOP

  2. Objectives • Learn more about the history of our understanding of the universe. • Spring cleaning

  3. Late Labs • Remember to turn in your late labs! • You’re losing points every day they’re late!

  4. Cosmos Episode Three • Pre-video questions • What does “Cosmos” mean? • The universe seen as a well-ordered whole • What did Robert Hooke discover? • What did Newton discover? • What did Halley discover? • What is a “light-year”?

  5. New Bellringers • If you’re absent or late you need to see me ASAP to make up the bellringer. • I will enter the grades once a week.

  6. Cosmos Episode Three • How has our natural ability for pattern recognition helped and hindered societal advancements? • Why was it so difficult for Halley to publish Newton’s work? • Why was it so important for Newton’s work to be published and how did it help to predict the future? • What were three scientific discoveries or inventions that Halley made? • Describe what will happen when the Milky Way and Andromeda galaxies finally meet up.

  7. Bellringer – 2 mins to hand in • A 53kg boy is held at rest on a swing that is 1.5m above its lowest point. What is the boys maximum velocity as he swings through his lowest point? DO WORK STOP

  8. Objectives • Finish Cosmos Video • Understand how sound waves travel.

  9. Cosmos Episode Three • How has our natural ability for pattern recognition helped and hindered societal advancements? • Why was it so difficult for Halley to publish Newton’s work? • Why was it so important for Newton’s work to be published and how did it help to predict the future? • What were three scientific discoveries or inventions that Halley made? • Describe what will happen when the Milky Way and Andromeda galaxies finally meet up.

  10. Bellringer – 2 mins to hand in • Explain how the total mechanical energy of a swinging pendulum is conserved. DO WORK STOP

  11. Objectives • Learn the basics of sound waves. • Act like a bat and use sound waves to calculate dinner time.

  12. Sound Waves

  13. What does sound do for us?

  14. Making Sound • Put your fingers against your throat and then hum. What do you feel? • As your vocal cords move forward, air particles are driven forward and create high pressure. • As your vocal cords move backwards they create low pressure.

  15. Making Sound

  16. Making Sounds

  17. Small Slinky Demo • Which direction does a high pressure want to move? • Which direction does a low pressure want to move? • Does the slinky move or vibrate?

  18. Making Sound • Collisions of the low and high air pressure areas cause the variations to move from the tuning fork in all directions. • If you were to focus on one spot, you would see the value of the air pressure rise and fall.

  19. Describing Sound • A pressure oscillation that is transmitted through matter is a sound wave! • Sound waves travel through air because a vibrating source produces regular variations, or oscillations, in air pressure.

  20. Describing Sound • Sound waves are longitudinal waves because the motion of the particles in air is parallel to the direction of the wave’s motion. • The frequency of a sound wave is the number of oscillations in pressure per second. • The wavelength is the distance between successive regions of high pressure or low pressure.

  21. Describing Sound • Just like any other wave the speed of sound depends on the medium through which it is traveling. • Air temperature changes the speed of sound, increasing about .6m/s for every 1 degree Celsius increase.

  22. Sound Through Different Mediums • Let’s Race: Solid vs. Gas! • In general the speed of sound is greater in solids and liquids than in gases.

  23. Sound Without a Medium • What happens if we remove the medium for sound to travel through? • Demo Time! • Write down what you observe!

  24. Properties of Sound Waves • Sound waves share the general properties of other waves! • Sound waves can reflect off of hard surfaces, such as the walls of a room, or the bottom of a well. • Reflected sound waves are called “Echoes”.

  25. Echoes • If you know the speed at which a sound wave is traveling you can calculate how far away you are from something by timing how long it takes a sound wave to leave you, bounce off of something, and then return back to you. • Bats, some cameras, and ships with sonar use this idea!

  26. Echoes • Bats call it echolocation. • Dolphins call it echolocation. • Submarines call it sonar (SOund Navigation And Ranging).

  27. Sonar

  28. Sonar • https://www.youtube.com/watch?v=-fAAxEIFeLU • How has sonar helped scientists save fish populations? • How has sonar helped scientists gather information about the bottom of the ocean?

  29. Sonar

  30. Echolocation • https://www.youtube.com/watch?v=bAvoz_ofoeo

  31. Echolocation and Sonar Practice • Sound waves travel at about 1,484m/s in water, and about 343m/s in air. • If a bat counts 0.013 seconds between releasing a sound wave and then hearing it return, how far away is its dinner? • d=4.5m • However the bat’s dinner is only 2.25 meters away because 4.5 meters is the distance the sound waves travels back and forth between the bat and the dinner.

  32. Echolocation and Sonar Practice • Sound waves travel at about 1,484m/s in water, and about 343m/s in air. • If a submarine spots a large blip on its sonar are screen that is 0.25s away, how far away is danger? • 185.5 meters • If a dolphin hears Nemo o.oo1s away, how far away is the end of Nemo? • 0.75 meters

  33. Bellringer – 2 mins to hand in • How far away is the whale from the shore if it measures a time of 0.52 seconds between emitting and hearing the sound wave return from the shore? DO WORK STOP

  34. Objectives • Practice your sonar skills • Learn and explain sound wave interference • Learn the different ways of detecting sound

  35. Echolocation and Sonar Practice • What is the speed of sound in a mystery liquid if the sonar gun records a time of 0.5 seconds between being sent out, reflecting off a target 125 meters away and then returning?

  36. Sound Wave Interference • Like other waves, sound waves can interfere with each other when they meet. • Will constructive interference make the sound louder or weaker? • Which will have a greater volume, a node or an antinode?

  37. Sound Wave Interference

  38. Sound Interference Demo • https://www.youtube.com/watch?v=qfJw1_vEKFo • Warning: This may cause severe headaches.

  39. Surround Sound • Take a piece of paper and roll it into a tube. • Is the sound really only on one side? • Your brain calculates the time difference between both of your ears hearing the same noise to figure out which direction that noise came from.

  40. Surround Sound Headphones • https://www.youtube.com/watch?v=oPTa4_HrPhs • How do they calculate the time differences? • They just record with two microphones about a head width apart. Your brain does all the timing calculations!

  41. Listening

  42. Sound Detectors • Sound detectors transform sound energy (KE of vibrating particles of the medium) into another form of energy. • Microphones transform the energy into electrical energy. • How do you think microphones convert kinetic energy into electrical energy?

  43. Microphones • Waves and electromagnetism! • It’s like a speaker in reverse.

  44. The Human Sound Detector • We don’t have coils and magnets in our ears, but we can still convert the vibrating energy in the air into a different form of energy. • Simply, our eardrum is shook by the vibrating air, then the eardrum shakes very tiny auditory bones which transfer these vibrations into the fluid in the cochlea. There are nerves in the fluid that pick up these vibrations and send them to the brain to be interpreted.

  45. The Ear

  46. The Broken Ear • Your eardrum is a membrane that is meant to keep stuff from slipping into your head…it can be broken  • Like most of your body it will heal if ruptured.

  47. What Can We Hear? • Our ears can’t hear every sound! • On average people can hear between 20Hz and 20,000Hz • https://www.youtube.com/watch?v=qNf9nzvnd1k • So what happens as 5Hz or 50,000Hz? • If tones are at a higher volume and “pure” we can hear more.

  48. Animals for the win! • Many animals, such as dogs, cats, elephants, dolphins, whales, and bats, are capable of hearing sounds at frequencies that humans cannot hear. • Low frequencies travel further than higher frequencies because lower frequencies have less air friction.

  49. Bellringer – Not Collected • What is the frequency range of the average human?

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