# AAMC 5 PS item 9

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#### EnginrTheFuture

##### Full Member
If ocean waves strike the shore every 3 s and the horizontal distance between adjacent crests and troughs is 1 m, what is the average speed of the waves?

A. 0.33
B 0.66
C
D

I realize how/why the answer is what it is. BUT...

Did anyone else interpret this as the distance between adjacent troughs = 1m? I think the wording here ambiguous and lead to a really worthless mistake. Mid-exam I thought the same thing... "which do they mean?". I ended up going with the distance between troughs (an entire wavelength) being 1 m rather than the difference from crest to trough being 1m. Just wondering if this was glaringly obvious to others or not.

#### MrNeuro

##### Full Member
7+ Year Member
If ocean waves strike the shore every 3 s and the horizontal distance between adjacent crests and troughs is 1 m, what is the average speed of the waves?

A. 0.33
B 0.66
C
D

I realize how/why the answer is what it is. BUT...

Did anyone else interpret this as the distance between adjacent troughs = 1m? I think the wording here ambiguous and lead to a really worthless mistake. Mid-exam I thought the same thing... "which do they mean?". I ended up going with the distance between troughs (an entire wavelength) being 1 m rather than the difference from crest to trough being 1m. Just wondering if this was glaringly obvious to others or not.

yeah i changed it to their interpretation first then changed it back after reading it like 10 times

it should be

"between an adjacent crest and trough"

#### folktale

##### Full Member
If ocean waves strike the shore every 3 s and the horizontal distance between adjacent crests and troughs is 1 m, what is the average speed of the waves?

A. 0.33
B 0.66
C
D

I realize how/why the answer is what it is. BUT...

Did anyone else interpret this as the distance between adjacent troughs = 1m? I think the wording here ambiguous and lead to a really worthless mistake. Mid-exam I thought the same thing... "which do they mean?". I ended up going with the distance between troughs (an entire wavelength) being 1 m rather than the difference from crest to trough being 1m. Just wondering if this was glaringly obvious to others or not.

Ehh, didn't really think of it that way. Adjacent crests and troughs meant crest and trough to me. I know what you mean, but if they meant it like that, they wouldn't have really placed those two side by side b/c that'd be tricky in that case.

#### typicalindian

##### Full Member
5+ Year Member
7+ Year Member
Yeah I made the same mistake, was pretty annoyed at that question

#### BestDoctorEver

##### Membership Revoked
Removed
5+ Year Member
If ocean waves strike the shore every 3 s and the horizontal distance between adjacent crests and troughs is 1 m, what is the average speed of the waves?

A. 0.33
B 0.66
C
D

I realize how/why the answer is what it is. BUT...

Did anyone else interpret this as the distance between adjacent troughs = 1m? I think the wording here ambiguous and lead to a really worthless mistake. Mid-exam I thought the same thing... "which do they mean?". I ended up going with the distance between troughs (an entire wavelength) being 1 m rather than the difference from crest to trough being 1m. Just wondering if this was glaringly obvious to others or not.
The answer is B...right? v = lambda/T = 2m/3s = 0.66 m/s...because adjacent means next to each other...therefore, the wavelength = 2m.

#### EnginrTheFuture

##### Full Member
The answer is B...right? v = lambda/T = 2m/3s = 0.66 m/s...because adjacent means next to each other...therefore, the wavelength = 2m.

Yep, you're right. I just thought adjacent troughs and crests meant one trough to the next and one crest to the next.

Removed
Edit: Wrong!

Last edited:

#### folktale

##### Full Member
It does mean one trough to the next trough and one crest to the next crest. That's why the wavelength is 2m and not 1m. 1 wavelength is trough to crest, not crest to crest or trough to trough.

I don't agree with this.

#### pfaction

##### Full Member
10+ Year Member
I think he meant to say one meter.

#### MedPR

##### Membership Revoked
Removed
Came back to correct myself, but see that a couple of people already caught it. 1 wavelength = crest to crest/trough to trough, but the question indicates that 1m is half a wavelength, making the wavelength 2m.

#### folktale

##### Full Member
Came back to correct myself, but see that a couple of people already caught it. 1 wavelength = crest to crest/trough to trough, but the question indicates that 1m is half a wavelength, making the wavelength 2m.

Yea, you might want to edit your other post and change 1 wavelength to 1m b/c that was wrong for sure. But I know what you're saying.

#### young_gohard

##### New Member
5+ Year Member
Good to know I wasn't the only one tripped up by that language.