time sound to travel= distance/velocitysound
time for train get to the speed of v
v=V0+at
solve for t.
This is in reply to a previous post, I'm not really sure whether replies to posts that are several days old are viewed by anyone, so I'm reposting just in case.
In reply to bobpursley's post,
I just want to ask, how would you know how long it takes for the sound to reach you? Would you multiply the time it took for the frequency to decrease by 2, to find the total time?
Homework Help Forum: Physics - Frequency
Posted by Intensity on Monday, January 25, 2010 at 8:43pm.
While blowing its horn of frequency 580 Hz, a car accelerates at 0.4 m/s2.
The car starts from rest by your side and moves away.
How long will it take for the frequency you hear to decrease by 5%?
Hint: Do not forget to include the time it will take for sound to reach you.
* Physics - Frequency - bobpursley, Monday, January 25, 2010 at 8:47pm
figure the velocity the car has to go to drop the sound by 5Percent. then, figure the time to get to that speed, then add the time it takes sound to travel that same distance back to you.
2 answers
How long will it take for the frequency you hear to decrease by 5%?
This is what I have done so far:
I found the speed of the car by using this equation:
f2=f1(340/340+Vsource) ; f2/f1 = 0.95 (..since the frequency is decreasing by 5%)
Next, I used this speed and the acceleration given to find the time it took for the frequency to decrease this much.
From what you are saying above I understood that you wanted me to find the distance the car travelled during this time and use that distance to see how long it took the sound to reach us?
This is what I ended up using, but I don't think it's right.
(V2)^2 = (V1)^2 + 2ad
t = d/V ; where V = 340 and t was my final asnwer..
I think that since we're talking about a wave and its parameters as the sound reaches us; my method would be inappropriate?
Please help if it's possible!
This is what I have done so far:
I found the speed of the car by using this equation:
f2=f1(340/340+Vsource) ; f2/f1 = 0.95 (..since the frequency is decreasing by 5%)
Next, I used this speed and the acceleration given to find the time it took for the frequency to decrease this much.
From what you are saying above I understood that you wanted me to find the distance the car travelled during this time and use that distance to see how long it took the sound to reach us?
This is what I ended up using, but I don't think it's right.
(V2)^2 = (V1)^2 + 2ad
t = d/V ; where V = 340 and t was my final asnwer..
I think that since we're talking about a wave and its parameters as the sound reaches us; my method would be inappropriate?
Please help if it's possible!