Fluids Question Regarding Density

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Homework Help Overview

The problem involves a spherically shaped balloon filled with helium, with a specific radius and mass, and seeks to determine the maximum cargo it can lift while neglecting the buoyant force on the cargo itself. The subject area relates to fluid mechanics and buoyancy principles.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to calculate the buoyant force using a specific equation but expresses confusion over the results. Other participants question the formulation of the buoyant force equation and suggest drawing a free-body diagram to clarify the forces involved.

Discussion Status

Participants are actively engaging with the problem, with some offering guidance on the need for a free-body diagram and a clearer understanding of the forces at play. There is no explicit consensus on the correct approach yet, as participants are exploring different interpretations of the buoyant force equation.

Contextual Notes

Participants are working under the assumption that the buoyant force must balance the weight of the balloon and the cargo, and there is a noted confusion regarding the units in the equations being used.

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Homework Statement



A spherically shaped balloon has a radius of 11.5 m, and is filled with helium. How large a cargo can it lift, assuming that the skin and structure of the balloon have a mass of 1200 kg?
Neglect the buoyant force on the cargo volume itself.

Homework Equations


Fb = (Mhe+800kg)g


The Attempt at a Solution


I used the above equation to determine the buoyant force acting on the balloon but didn't seem to work. I tried some other methods but i can't get how much it can lift. Need some explanation thanks.
 
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What's the equation for the buoyant force on ANY object in ANY fluid? After getting that, draw a free-body diagram on the balloon and note that buoyancy must balance gravity if the balloon is to lift the heaviest possible load.
 
still can't get it...seems like a easy question too.. i am setting Fb = 1200+m+g. I got force buoyant to be density of air (1.29 kg/m3) * Gravity * Volume. Which looks like 1.29*9.8*3583.477 = 1200+m+g. m is the mass of the cargo which i am solving for. i keep getting the mass of the cargo to be 3422.68 which is wrong. any ideas of where I'm messing up?
 
where did you get Fb=1200+m+g? It doesn't make sense because m has units of kg, while g has units of m/s^2.

Anyhow, draw a free-body diagram. Label all forces. Then write out Newton's second law. Don't take any shortcuts until you get more familiar with physics.
 

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