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Waves Videos 15 videos

AP Physics 1: 1.3 Waves
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AP Physics 1: 2.2 Waves 19 Views


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Description:

AP Physics 1: 2.2 Waves. What's the wavelength of this standing wave?

Language:
English Language

Transcript

00:03

And here's your sure shmoop du jour brought to you by music because [Woman sat at a desk with open books]

00:07

without waves of sound well they're just wouldn't be music hopefully your brother

00:10

just going through a phase with those drums a standing wave is generated by a [Girls brother playing the drums]

00:15

string that is 24 meters long and attached to one end of a wall the

00:21

unattached end of the string is then moved up and down to induce a wave

00:25

motion with a total of six anti-nodes what's the wavelength of this standing

00:31

wave and here the potential answers...All right well to answer this

00:37

question let's take a closer look at standing waves but not too close [Girl looking at a moving string]

00:41

it's the vibrating string and we don't want to get smacked let's imagine the same setup

00:45

with a string anchored on the wall and us creating a wave at the other end but [Man holding a piece of string attached to a wall]

00:50

this time we'll just send one wave down the string when the wave reaches the [One wave created down the string]

00:54

wall it'll bounce off reflecting back down the string now if we find the right

00:59

frequency the wave we create at one end will perfectly match the way that

01:04

reflects off the wall when this happens we'll create a standing wave right well [A standing wave of the piece of string]

01:09

a standing wave is created by two waves moving in opposite direction to create

01:13

constructive interference of their points of maximum amplitude and

01:17

destructive interference at their points of equilibrium this creates a standing

01:22

wave which vibrates back and forth with its anti node but doesn't move at all at [Standing wave shown vibrating back and forth]

01:28

it nodes. Well the wavelength of a standing wave equals the length of two

01:33

complete loops formed by the nodes and antinodes. Why two? well since we're dealing

01:37

with two waves acting in conjunction the wavelength has to include the crest and [Crest and trough of a wave]

01:42

trough of the wave ok thanks for learning about standing waves with us

01:46

we've certainly had a lot of fun and oh yeah we haven't answered the question. [Pieces of wood attach to spell The End]

01:50

Well let's do some math the length of the string equals the number of anti

01:54

nodes multiplied by the distance between each anti node and the distance between

01:58

each antinode equals half of a wavelength so the equation looks like

02:03

this right here now we just have to put in the numbers and solve for the [Equation for wavelength of the string]

02:06

wavelength. A length of the string is 24 meters and we have six nodes with this

02:11

we're able to see that the wave length equals 8 meters so the answer is B just

02:15

remember that the wavelength in a standing wave equals the length of one wave gone [A standing wavelength]

02:19

from equilibrium to maximum positive displacement then back to equilibrium

02:22

down to maximum negative displacement and finally back to equilibrium phew, getting a [a rollercoaster in motion]

02:28

little seasick here describing it like that, and if our brother keeps listening to

02:31

the top songs of the year and at that volume well we're going to

02:35

go in there and explain all this standing wave stuff to him in great detail [girl explaining standing waves to her brother playing the drums]

02:39

well that should keep him quiet for a while

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