Solving for Car Mass with Gauge Pressure and Surface Area | Physics Problems

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Homework Help Overview

The discussion revolves around fluid mechanics problems, specifically focusing on gauge pressure in tires, buoyancy, and density calculations related to various objects, including a car and a balloon. Participants explore the relationships between pressure, force, area, and mass, as well as the principles of buoyancy and density in different contexts.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Problem interpretation, Assumption checking

Approaches and Questions Raised

  • Participants discuss converting units of pressure and area, applying the formula for pressure to find mass, and the implications of multiple tires supporting the weight of a car. There are attempts to understand buoyant force and how to calculate it based on the volume of a balloon and the densities of helium and air. Questions arise about how to relate the apparent mass of a submerged object to its density and how to calculate the density of an unknown metal using buoyancy principles.

Discussion Status

Some participants have offered guidance on unit conversions and the application of formulas, while others are exploring different interpretations of the problems. There is a productive exchange of ideas regarding the calculations needed for both the car mass and the buoyancy of the balloon, although not all participants agree on the methods or results. The discussion remains open with various lines of reasoning being explored.

Contextual Notes

Participants note the complexity of the problems and the need for careful unit conversions. There is also mention of specific assumptions, such as neglecting certain forces in buoyancy calculations and the importance of understanding the relationship between mass, volume, and density in fluid mechanics.

  • #31
jrd007 said:
Isn't bouyancy force = pVg? - I know neither p(denisty) or volume or the Fb so how can I solve for it?
The fluid is water, so you should know the density. Also: true weight - buoyant force = apparent weight.
 
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  • #32
denisty of water is 1000 kg/m^3

So since mass is 63.5 I just divide that by the volume and tha give me density?
 
  • #33
Yes. Once you figure out the volume you can get the density by \rho = m/V. (Be careful with units.)
 
  • #34
yes but is it not jus 63.5/1000 ? I thought that was why I was trying to find the volume of water?
 
  • #35
1000 kg/m^3 is the density of water, not the volume of water displaced. (You'll need the density and the buoyant force to solve for the volume.)
 
  • #36
Actually you you can just minus the two to get the water displaces and change it into kg = .0081

63.5/.0081 = 7839! :)
 

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