Lect_31 - Energy. Intensity. Interference

Lect_31 - Energy. Intensity. Interference - Lecture 31...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
Lecture 31 Energy. Intensity. Interference. Beats.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
ACT: A sixth sense? A large ammunition factory and a town are separated by a rocky hill, at a horizontal distance of about 5 km. An accident produces a huge explosion in the middle of the night. What do the town folks experience? A. First the room shakes, and then they hear an explosion. B. First they hear an explosion, and then the room shakes. C. They hear an explosion and the room shakes at yp the same time.
Background image of page 2
5 km Time for sound wave to reach the town: Through hill (granite): Through air: 5000 m 0.8 s 6000 m/s x t v == = 14.6 s 343 m/s = granite granite Y ρ ⎛⎞ ⎜⎟ ⎝⎠ 14 seconds later! This happened in California during WWII. Most people woke up (distressed…) to the light quake and then heard the explosion. Many ttributed this to a “sixth sense” that had warned them of the imminent attributed this to a sixth sense that had warned them of the imminent disaster. The “sixth sense” was just the laws of wave propagation…
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Wave energy ork is clearly being done: > as hand Work is clearly being done Fdr 0 as hand moves up and down. • This energy must be moving away from your hand (to the right) since the kinetic energy (motion) of the end of the string grabbed by the hand stays the same. P
Background image of page 4
Transfer of energy The string to the left of x does work on the string to the right of x, just as your hand did: x Energy is transferred or propagated.
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Power Energy of a mass in SHM (attached to a spring k) Energy of a mass n SHM (attached to a spr ng k) 22 2 1 2 Ek A ω =∝ 2 k m ⎛⎞ = ⎜⎟ ⎝⎠ This energy propagates at speed v.
Background image of page 6
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 23

Lect_31 - Energy. Intensity. Interference - Lecture 31...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online