Can someone help me with this physics problem??

Question

A hiker tosses a rock into a canyon. He hears it strike water 4.78 s later. How far down is the surface of the water?

The speed of sound is Vs=343m/s.
I'm not sure how to start it..

Answer 1

Basically, use all of the equations that you know for the journey of the rock to the surface of the water and the journey of the sound of the splash back up to your ears. Solve for 't' in both of these equations. The sum of the 't's in both equations is 4.78s.

Suppose 'x' is the distance to the surface of the water.
distance formula:
x = x0 + (v0)t + (1/2)at^2

x0 and v0 are both zero since the rock at x=0 and at rest when you drop it.
a= 10m/s^2 (due to gravity)
so...
x = (1/2)(10)t^2

solve for t...
t = sqrt(1/5 x)


Now, sound moves at a constant velocity, so to solve for the time the sound travels from the water back up to your ears, use the average velocity formula:

v = xt
where v = 343 m/s
so...
t = 343 / x


Combine the two equations for t:
4.78s = sqrt(1/5 x) + 343/x

now solve for x....

Answer 2

The time elapsed is the time it took the rock to fall plus the time it took the sound to come back. You know the acceleration of gravity is 32 ft per second squared. The distance divided by the acceleration of gravity, plus the distance times the speed of sound, will equal 4.78 seconds.

Answer 3

h =1/2gt^2 (free fall)
t+343h=4.78 These are the equations to start with

Answer 4

First, ignore the fact of the dropping of the stone. Next, use the formula D=RT where Distance=velocity (Rate) times Time. You must use similar values such as meters/second and seconds in your calculations and answer in meters. I'll let you do the math.

Answer 5

Or post it in the physics category.

Or better yet, homework help.

Answer 6

Try this http://www.physics.com

Answer 7

it accelerates at a rate of 9.8 meters per second.
so d= a*t.

so... it is 9.8 x 4.78

nvm i messed up :-)