# Homework Help: Tank position problem based upon sound of fire

1. Dec 12, 2008

### brick

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

An approaching tank fires at you and you hear the sound 3 seconds after the muzzle flash. Ten seconds later the same tank fires again and you hear the sound 2 seconds after the flash. The temperature is 100 degrees Celsius. How fast is the tank going? How long until he reaches you.

2. Relevant equations

v=331.4 + .606Tc that is the speed of sound in air based upon the temperature.
v= wavelength symbol X frequency
These are the only ones i think that could help me but i could be mistaken.

3. The attempt at a solution

So i know the speed of sound in air is 392 meters/sec based upon the equation v=331.4 + .606Tc

v= 331.4 + .606(100)
v= 331.4 + 60.6
v= 392 m/s

I can't figure out where to go from here. to get the other answers thank you for any help

2. Dec 12, 2008

### LowlyPion

Welcome to PF.

First of all you might want to check the ambient temperature of the terrain, because 100° C is a prodigious life stopping temperature. 100° F maybe?

In any event ...

At the first shot the speed of the bullet lagged the firing by 3 seconds. In 10 seconds later it lagged by 2.

So ...

In 10 seconds the tank covered the distance that sound covered in 3 - 2 = 1 seconds. The rank is traveling then at 1/10 the speed of sound.

Resolve the temperature and you should be on the sunny side of the street.