# Homework Help: Volume/Displacement Problem

1. Dec 17, 2007

### j_suder2

1. The problem statement, all variables and given/known data
A Mississippi river barge is 65m long and 20m wide. How far will it sink into the water when 3000 tonnes of coal is placed on it?

2. Relevant equations
rho=m/v, L x W = A,

3. The attempt at a solution

I figured out the area of the barge in contact with the water, then converted the tonnes to kilograms. I used this to get the volume of coal taken off. (I think that works).
I guess from here I need to use the density of water to see how much is displaced by that amount of coal, and then determine the height of water this would correspond to.
I'm stuck at this last part.

2. Dec 17, 2007

### Shooting Star

Weight of water displaced = weight of coal, which means,
Volume displaced of water (not coal) X density of water = weight of coal.

Density of water can be taken to be 1000 kg/m^3.

3. Dec 17, 2007

### j_suder2

Ok so I can find the volume of water, I'm still having trouble finding the height of the displacment,
Thanks

4. Dec 17, 2007

### Shooting Star

Height*length*width = voulme.

5. Dec 17, 2007

### j_suder2

Thanks,
I just had the wrong conversion from tonnes to kg's