# Frequency of bobbing raft

1. Nov 12, 2006

### lizzyb

Hi - I'm not sure where to begin with this question:

Question:
A 4 m by 11 m raft whose mass is 17600 kg floats in fresh water. A 4990 kg load is dropped on the raft.

The acceleration of gravity is 9.8 m/s2 .

With what frequency does the raft bob up and down?

Answer in units of Hz.

Comments:

??

2. Nov 13, 2006

### lizzyb

ok I can use archimedes' principle regarding buoyancy force to determine how far the raft is depressed from it's initial equilibrium position below the surface to the water to the distance below the water when the load is dropped on it, but what then?

3. Nov 13, 2006

### lizzyb

frequency = $$\frac{1}{2 \pi} \sqrt{\frac{\rho A g}{m}}$$

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