Homework Help: How many people can the raft hold physics problem

1. Oct 4, 2008

Elvis

CAN ANYONE HELP ME, PLEASE ! I DON'T KNOW HOW TO SOLVE THIS PROBLEM

A raft is made of 10 logs lashed together. Each is 30cm in diameter and has a length of 5.5m. How many people can the raft hold before they start getting their feet wet,assuming the average person has a mass of 70 kg? Do not neglect the weight of the logs! Assume the specific gravity of wood is 0.60.

SG=0.60
r=1/2*30=15cm

I know
F/A = mg/A
F= mg =pAHg were p-->density
p=m/v
pressure=P=F/A

2. Oct 4, 2008

Staff: Mentor

Re: Fluids

Hint: What's the buoyant force acting on a completely submerged log?

3. Oct 4, 2008

Elvis

Re: Fluids

The boyanty Force is:

Fb = F2 - F1
pfgA(h2-h1)
pfgAh
pfgV

I don't know how to solve please help !

4. Oct 4, 2008

Staff: Mentor

Re: Fluids

The buoyant force is the weight of the displaced fluid. How much water does a submerged log displace?

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