# Homework Help: Sound waves

1. Feb 26, 2010

### tanzerino

1. The Young's modulus for tin is 4.5x10^10. If the speed of sound in tin is measured to be 2.73km/s , find its density in (kg/m^3) .

a)6.05x10^3
b)23.8x10^3
c)6.35x10^3
d)24.5x10^3
e)6.65x10^3

, E(tin)=4.5x10^10 ,speed of sound in tin=2.73km/s

2. v=sqrt(B/density) -where B is bulk modulus

3. if i substitute B as young's modulus I get answer a) in the choices.

What is difference between bulk modulus and young's modulus and if there is what relation relates them.Thanks.

2. Feb 26, 2010

### rl.bhat

Bulk modulus = 3*young's modulus.

3. Feb 26, 2010

### tanzerino

But when i substitute v=sqrt(3Y/density)=sqrt(B/density) i dont get an answer from choices while i do if i substitute v=y/density.is it possible that in sound waves the velocity is proportional to youngs modulus instead of bulk modulus as in other cases.

From serway :"For longitudinal sound waves in a solid rod of material, for example, the speed of
sound depends on Youngâ€™s modulus Y and the density !. Table 17.1 provides the speed
of sound in several different materials"

4. Mar 1, 2010

### tanzerino

any idea anybody?

5. Mar 1, 2010

### rl.bhat

While calculating the velocity of sound in solid, if the solid is a thin rod, the bulk modulus is replaced by Young's modulus.

6. Mar 1, 2010

### tanzerino

thanks very much.