2 Sound waves reflection easy problems

[Clara Chung]

Homework Statement

Refer to the photos, question 21 and 22(the one with a helicopter)

Homework Equations

Both answers are A

The Attempt at a Solution

for question 21, if the counts to ten, there are 9 intervals. I divide 20 by 9 and divide it again by 2 and get 1.1s not 0.5s.
for question 22. I think it is C. Because the first reflected pulse has traveled 2h and the second reflected pulse has traveled 4h. I think it is impossible for the answer to be A, the pulse should travel slower in water.

 

[lewando]

For Q21, if the first clap is associated with the count of zero, wouldn't there be 10 intervals?
For Q22, the speed of sound in water is greater than the speed of sound in air.

 

[Clara Chung]

For Q21, if the first clap is associated with the count of zero, wouldn't there be 10 intervals?
For Q22, the speed of sound in water is greater than the speed of sound in air.

But 20/10(2) = 1s?

 

[lewando]

That is true. That result matches answer B. I can't see how A could be correct.

 

[lewando]

Actually I misread the question. Only claps are being counted.

 

[Clara Chung]

Actually I misread the question. Only claps are being counted.

Oh thanks I can do it now