Projectile motion in one dimension

[NogginBoink]

Originally posted by: Heisenberg
The total time is takes for him to hear the sound will be the time of fall plus the time it takes for the sound to reach him. You'll then also have an expression for the distance in terms of the fall time and the time for the sound to reach him. Two equations and two unknowns, which should be solveable. I think that will work - gimme a minute to really think about it.

Uh... lessee here....

acceleration due to gravity: d= 1/2 a t^2

so

t^2 = d / (1/2 a)

or

t^2 = 2 d / a

or

t = sqrt (2 d / a)

a = 9.8 m/s/s, so

t = sqrt (2d/9.8)
t = sqrt (d/4.9)
++++++++++++++++++++++
speed of sound:

d = speed * time
d = 340 meters/sec * time
d = 340 * t
t = d/340
++++++++++++++++++++++

Now, the distance the modem fell is equal to the distance the sound traveled back. And we know the total time. So:

4 seconds = d/340 + sqrt(d/4.9)


aaarrrgghhh.... brain hurts! haven't done quadratics on forever!

That's as far as I can get without a textbook. 🙁

 

[NogginBoink]

Whew! My equation agrees with notfred's answer! I'm not a nutcase!

(Okay, well, at least not for my math skills, anyway.)

 

[Joemonkey]

This is why i hate physics... all the equations in the world don't matter because you aren't taking into account:

Air Density

Air Resistance from the Modem

those 2 make very small differences in your answer, but still make a difference!!

If the air is very dense, the sound will come up faster than if it was very thin

if the modem was dropped by holding on end of it and it went straight down like a blade, it would hit faster than if you dropped it while holding it like a tray, due to more air resistance...

 

[BennyD]

i know how to make sure

take a bucket of modems, a stopwatch and a cherry picker and find out 😛

 

[DaiShan]

Originally posted by: Heisenberg
The total time is takes for him to hear the sound will be the time of fall plus the time it takes for the sound to reach him. You'll then also have an expression for the distance in terms of the fall time and the time for the sound to reach him. Two equations and two unknowns, which should be solveable. I think that will work - gimme a minute to really think about it.

Wait your nick is heisenberg and you can't come up with the answer?!?!

 

[NogginBoink]

Originally posted by: DaiShan

Originally posted by: Heisenberg
The total time is takes for him to hear the sound will be the time of fall plus the time it takes for the sound to reach him. You'll then also have an expression for the distance in terms of the fall time and the time for the sound to reach him. Two equations and two unknowns, which should be solveable. I think that will work - gimme a minute to really think about it.

Wait your nick is heisenberg and you can't come up with the answer?!?!

Give him a break... he's just uncertain!

(*ducks the rotten tomatos being thrown*)

 

[Joemonkey]

Originally posted by: NogginBoink

Originally posted by: DaiShan

Originally posted by: Heisenberg
The total time is takes for him to hear the sound will be the time of fall plus the time it takes for the sound to reach him. You'll then also have an expression for the distance in terms of the fall time and the time for the sound to reach him. Two equations and two unknowns, which should be solveable. I think that will work - gimme a minute to really think about it.

Wait your nick is heisenberg and you can't come up with the answer?!?!

Give him a break... he's just uncertain!

(*ducks the rotten tomatos being thrown*)

OMFG best pun EVAR!

 

[CubicZirconia]

all the equations in the world don't matter

You still need to understand the basic principles. Adding in factors like air resistance just needlessly complicated things.

 

[her209]

The answer is 0 because distance does not exist in the 1st dimension.

 

[Woodchuck2000]

Originally posted by: her209
The answer is 0 because distance does not exist in the 1st dimension.

Yes it does. It's just in one dimension.