How much ice to float a 80 Kg person

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SUMMARY

The discussion focuses on calculating the volume of ice required to float an 80 kg person in salt water, with specific densities of salt water at 1025 kg/m³ and ice at 917 kg/m³. The key equation used is F_b = P_f * V_f * G, where F_b represents the buoyant force, P_f the density of the fluid, V_f the volume of the fluid displaced, and G the acceleration due to gravity. The participants highlight the need to account for both the weight of the person and the weight of the ice in the buoyancy calculations, leading to the equation (Volume of ice * Density of Ice + 784 N) = Volume of ice * Density of Salt Water.

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Homework Statement



Find the volume of the smallest block of ice which when floating on salt water will carry a person of mass 80 Kg

Densities:

Salt Water = 1025
Ice = 917

Homework Equations



F_b=P_f * V_f * G

The Attempt at a Solution



I figured F_b would have to be equal to the force of the person down which is equal to 784 N. Then plugging that into the equation and solving for V_f I get .078. I used the Salt Water for P_f. Is there somewhere that I need to plug in Ice?
 
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Don't forget the weight of the ice...:wink:
 
ok so I tried to add the weight of ice in here is what I get.

like before I have the equation.

W_p * G = 784

This is the force of the pearson. Next I have

784 = Volume of the ice * Density of water * Gravity

Then to add in the weight of ice I do this.

Volume of the ice * Density of Ice * Gravity + 784 = Volume of ice * density of water * gravity

This makes an equation has everything cancel out.
What am I doing wrong?
 
iceman_ch said:
ok so I tried to add the weight of ice in here is what I get.

like before I have the equation.

W_p * G = 784

This is the force of the pearson. Next I have

784 = Volume of the ice * Density of water * Gravity

Then to add in the weight of ice I do this.

Volume of the ice * Density of Ice * Gravity + 784 = Volume of ice * density of water * gravity

This makes an equation has everything cancel out.
What am I doing wrong?

(vol ice*(density ice)+m)g=volume ice(density SALT water)*g Now the question is ice salty? I think not. On the left hand side we have the total weight of the ice plus man, on the right the weight of water displaced.
 

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