Pulse Question

1. Jan 30, 2016

OmniNewton

1. The problem statement, all variables and given/known data

2. Relevant equations
Refer to 3.

3. The attempt at a solution
My problem is the theory I am unsure how any equations apply to this problem. This seems bad that I have no attempt at solution but I am honestly unsure how to start or of any relevant equations.

2. Jan 31, 2016

ehild

Think instead of looking after equations. Imagine, you stand at distance d from a wall, and you clap once. The sound reflects from the wall. What time after the clap does the echo reach you?

3. Jan 31, 2016

OmniNewton

v=dt
so t = v/2d

4. Jan 31, 2016

ehild

You mean the time is the shorter the longer is the distance ???
And what is the time if the wall is at distance d+w?
What is the difference of times if one wall is at distance d and the other wall is w distance farther?

5. Jan 31, 2016

OmniNewton

Sorry about the delay I've been really thinking this through. I'm just unsure what is being said by difference of times.

6. Jan 31, 2016

ehild

The first of your problem is how do you get the time you need to cover a distance d with speed v. You travel with speed 100 km/h, what time is needed to reach a town at 200 km distance?

7. Jan 31, 2016

OmniNewton

2 hours

8. Jan 31, 2016

ehild

What is the general formula used to get time from distance and speed?

9. Jan 31, 2016

OmniNewton

d=vt
t = d/v

10. Jan 31, 2016

ehild

It is correct now. In what time does the echo of the clap return from a wall at distance d? And what is the time of return from a wall at distance d+w?

11. Jan 31, 2016

UchihaClan13

The time taken to return back(when the distance is d)
is equal to 2d/v where v is the velocity of sound
and when the distance is d+w
The time taken is 2(d+w)/v
Therefore
The difference in the times taken equals 2w/v

12. Jan 31, 2016

OmniNewton

Alright after looking at Uchiha's work that is correct. difference in time represents the period.

So,

f = 1/T = v/2w = 343 m/s/2(0.75m) = 230 Hz

for b) since f is proportional to 1 /w the frequency will be higher

13. Jan 31, 2016

UchihaClan13

Precisely,OmniNewton
Just some thinking and calculations always suffice :)

14. Jan 31, 2016

OmniNewton

Thank You So Much!

15. Jan 31, 2016

UchihaClan13

You're welcome!

16. Jan 31, 2016

UchihaClan13

Heh thanks mate for those likes!:)