# Homework Help: Question on Solids

1. Apr 10, 2010

### lifeiseasy

1. The problem statement, all variables and given/known data
A metal rod of length 1.0 m is hit with a hammer at one end. It takes 5.5x10^-4 s for the compression pulse generated to travel to the other end and reflected back to the end hit by the hammer. Find the Young Modulus of the metal.
(Given: density of the metal = 9.0x10^3 kg m^-3)

2. Relevant equations
E=FL/Ae
D=M/V

3. The attempt at a solution
D=M/V=M/(AxL) (L=1m)
I just don't know how to make use of the data given. Clueless. My head's gonna explode!

2. Apr 10, 2010

### Stonebridge

You need the equation that relates the speed of sound in a solid to its Young Modulus and density. From that you can calculate the modulus simply and directly from the other two values you are given.
Do you have this equation in your book or lecture notes?

3. Apr 10, 2010

### lifeiseasy

Yes! Is it v=[sq. root](E/D)?

Ah, it's actually just substituting numbers into the equation... Why can't I think of this equation in the first place

Thanks a lot!