# Buoyant Force on a man

1. Apr 24, 2017

### tennisgirl92

1. The problem statement, all variables and given/known data
A certain man has a mass of 85.0 kg and a density of 995 kg/m3 (exclusive of the air in his lungs).
(a) Calculate his volume.
.0854 m3
(b) Find the buoyant force air exerts on him.
N
(c) What is the ratio of the buoyant force to his weight?
(buoyant force / weight)

2. Relevant equations
Fb=density (of substance) x Volume (of object) x g
density of air=1.2 kg/m3

3. The attempt at a solution

Fb=(1.2 kg/m3) x (9.8) (.0854)
=1.004N

and then for part c
1.004/ (9.8 x 85=833)=.00121

For some reason this is incorrect. Does anyone see why?

2. Apr 24, 2017

### kuruman

Incorrect density.

Edit: Sorry I misread the question.

Last edited: Apr 24, 2017
3. Apr 24, 2017

### FactChecker

For the buoyant force of the displaced air, the air density should be used as the OP shows. How far off is the answer? Could it be just due to rounding of 1.225 to 1.2?

4. Apr 24, 2017

### tennisgirl92

Yes, I tried that as well and obtain 833N, which is also incorrect. I did this first, and then thought we need to use the density of the air.

5. Apr 24, 2017

### tennisgirl92

yes, I tried 1.225 and 1.2. Both are incorrect.

6. Apr 24, 2017

### FactChecker

Just so we don't have to keep guessing, what is the answer given?

7. Apr 24, 2017