G482- Wave speed help :) Watch

Super199
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Can someone help me with the following question

The frequency of a wave is 25Hz and the distance between P and Q is 1.8cm

Calculate:

The period of the wave:

I have done this by doing 1/25 and got 0.04s

The speed of the wave:

worth 3 marks. I know the formula wavespeed= Wavelength x frequency. But what is the wavelength? Is it 1.8cm?
Any help would be appreciated
Thanks in advance
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XMaramena
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So here we have a wave which cycles 25 times every second and is 1.8cm long.

I'm going to assume that P & Q are the start and end points. I would assume this if no diagram or additional info is given.

Let's use the SFL triangle: Speed = Frequency x Length, Frequency = Speed / Length, Length = Speed / Frequency.

We want to find out the speed of the wave, so we're going to use Frequency x Length. Here's how I would show the working out in an exam:

S: Speed; F: Frequency; L: Wavelength [cm]

Target: S
S = F x L
S = 25 x 1.8
25 x 1.8 = 45
S = 45 cm/s
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Super199
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(Original post by XMaramena)
So here we have a wave which cycles 25 times every second and is 1.8cm long.

I'm going to assume that P & Q are the start and end points. I would assume this if no diagram or additional info is given.

Let's use the SFL triangle: Speed = Frequency x Length, Frequency = Speed / Length, Length = Speed / Frequency.

We want to find out the speed of the wave, so we're going to use Frequency x Length. Here's how I would show the working out in an exam:

S: Speed; F: Frequency; L: Wavelength [cm]

Target: S
S = F x L
S = 25 x 1.8
25 x 1.8 = 45
S = 45 cm/s
mm I was going to do this but didn't realise 1.8cm was the wavelength. The two are pi out of phase so does this mean it is a wavelength when they have this difference?
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Joinedup
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(Original post by Super199)
mm I was going to do this but didn't realise 1.8cm was the wavelength. The two are pi out of phase so does this mean it is a wavelength when they have this difference?
can you post the graph?
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Super199
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(Original post by Joinedup)
can you post the graph?
Never mind I've done it now. Basically P and Q were pi out of phase and the wavelength was 2pi. So you times the 1.8 by 2 and go from there. Thanks anyway
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