kosh_ki
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#1
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Hi - can someone show me the correct way of doing this and where I went wrong?

My reasoning as below:
v = fl, v = 0.2m/s
D = vt; = 60 x 0.2 = 12 = 1200 cm
Hence D

But the answer is actually E.

Thanks.

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Stonebridge
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#2
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(Original post by kosh_ki)
Hi - can someone show me the correct way of doing this and where I went wrong?

My reasoning as below:
v = fl, v = 0.2m/s
D = vt; = 60 x 0.2 = 12 = 1200 cm
Hence D

But the answer is actually E.

Thanks.

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Views: 8
Size:  55.5 KB
The question is not asking how far the wave itself has travelled.
It's asking how far a particle of the medium has travelled in its motion up and down, say, while the wave moves horizontally.
The amplitude of 3cm means the particle travells a total of 6cm up and 6cm down on one oscillation.
From the frequency of the wave you can work out how many times it does that in one minute.
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LuigiMario
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#3
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consider this,

the particle is sitting bored in the medium,
then a wave uplifts it 3cm, then drops it 3cm to the zero, then drops it a further 3cm to the maximum opposite amplitude then brings it back 3cm up to the zero.
this happens 5 times per second
for a whole 60 seconds

so how far (ignoring direction) did the particle actually cumulatively move, whilst not going anywhere in other axes (is that another modulus?)
and that's probably your answer
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kosh_ki
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#4
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(Original post by LuigiMario)
consider this,

the particle is sitting bored in the medium,
then a wave uplifts it 3cm, then drops it 3cm to the zero, then drops it a further 3cm to the maximum opposite amplitude then brings it back 3cm up to the zero.
this happens 5 times per second
for a whole 60 seconds

so how far (ignoring direction) did the particle actually cumulatively move, whilst not going anywhere in other axes (is that another modulus?)
and that's probably your answer
(Original post by Stonebridge)
The question is not asking how far the wave itself has travelled.
It's asking how far a particle of the medium has travelled in its motion up and down, say, while the wave moves horizontally.
The amplitude of 3cm means the particle travells a total of 6cm up and 6cm down on one oscillation.
From the frequency of the wave you can work out how many times it does that in one minute.
thank you so much both! i'm just confused though because we seem to be taking 3cm as the height (the amplitude), but doesn't the wave have curves hence the amplitude/height doesn't take that into account?
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LuigiMario
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it's a narrowly focused question on what one particle of the otherwise undisturbed medium 'feels' It just goes up and down, knows nothing in a dimension beyond what it can feel, travelling waves are 2D/3D-time, but medium particle lives in a 1D/2D world (but that's how I see it) there might be a more classic answer also available
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