Leaping Off the 400-Year-Old Bridge in Bosnia

[mandy9008]

Homework Statement

In Bosnia, the ultimate test of a young man's courage used to be to jump off a 400 year old bridge (now destroyed) into the River Neretva, 23 m below the bridge. (a) How long did the jump last? (b) How fast was the jumper traveling upon impact with the river?
(c) If the speed of sound in air is 341 m/s, how long after the jumper took off did a spectator on the bridge hear the splash?

Homework Equations

a. and b. change in Y=Voy t - .5 gt²

The Attempt at a Solution

a. v=21.23 m/s
b. t=2.167s
c. Vy=Voy - gt
341 m/s =21.23 m/s - 9.8 m/s² t
t=-32.63s
I know that time cannot be negative, but I have tried the inverse of this number also, and I am still getting it wrong. Am I even using the correct equation?

 

[Doc Al]

a. v=21.23 m/s
b. t=2.167s

OK.

c. Vy=Voy - gt
341 m/s =21.23 m/s - 9.8 m/s² t
t=-32.63s
I know that time cannot be negative, but I have tried the inverse of this number also, and I am still getting it wrong. Am I even using the correct equation?

No, you are not. The sound travels through the air at a constant speed. (The sound is not a projectile.)

 

[mandy9008]

Could you point me in the right direction as to the equation I am supposed to use?

 

[Doc Al]

Could you point me in the right direction as to the equation I am supposed to use?

What equation relates speed, distance, and time for something moving at constant speed? That's what you'll need to find the time it takes for the sound of the splash to travel up to the bridge.

(To find the total time, don't forget to add in the time it takes for the man to fall, which you've already calculated.)

 

[rdl]

I would like to first clarify that the described activity of jumping off a 400-year-old bridge into a river can be extremely dangerous and should not be attempted without proper safety measures in place.

To answer the first question, we can use the equation d=Vit + 1/2at^2, where d is the distance, Vi is the initial velocity, a is acceleration (in this case, due to gravity), and t is time. Since the initial velocity is 0 (the jumper is starting from rest), we can simplify the equation to d=1/2at^2. Plugging in the given values, we get d=23 m and a=9.8 m/s^2. Solving for t, we get t=2.167 seconds.

To answer the second question, we can use the equation Vf=Vi+at, where Vf is the final velocity, Vi is the initial velocity, a is acceleration, and t is time. Again, since the initial velocity is 0, we can simplify the equation to Vf=at. Plugging in the given values, we get Vf=21.23 m/s.

For the third question, we can use the equation d=Vt, where d is the distance, V is the speed of sound, and t is time. We know the distance is 23 m and the speed of sound is 341 m/s, so we can solve for t. t=d/V=23 m/341 m/s=0.067 seconds. This is the time it takes for the sound of the splash to reach the spectator on the bridge. However, it is important to note that this calculation assumes that the sound travels in a straight line and does not take into account any potential obstacles or reflections that may affect the speed of sound.