Find the Apparent Weight: Solving for Volume

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SUMMARY

The discussion focuses on calculating the apparent weight of an object submerged in water using the buoyant force equation. The object weighs 0.442N in air and 0.037N when submerged. The volume of the object is determined to be 0.405m3 using the formula V = (W - Fb)/(ρg), where W is the weight in air, Fb is the buoyant force, ρ is the density of water (1000kg/m3), and g is the acceleration due to gravity (9.8m/s2). The apparent weight when submerged is calculated to be 3.96N.

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  • Understanding of buoyant force and Archimedes' principle
  • Familiarity with the formula for buoyant force: Fb = ρVg
  • Knowledge of basic physics concepts such as weight and density
  • Ability to perform unit conversions and algebraic rearrangements
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An object hanging in the air causes a scale to read 0.0451kg. When the object was submerged in water, the scale is balanced at 0.0370. I found the object of the weight in air to be 0.442N. The question is to find the apparent weight when submerged in water. How do I find the volume to find the apparent weight. So far, I have 0.442-(1000kg/m^3)(9.8m/s^2)(V)=W. What's the volume?
 
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I presume that by "apparent weight" is meant what the scale reads when the object is submerged. You measured the apparent weight directly, so what are you calculating?
 


To find the apparent weight when submerged in water, you will need to use the buoyant force equation, which is given by Fb = ρVg, where Fb is the buoyant force, ρ is the density of the fluid (in this case, water), V is the volume of the object, and g is the acceleration due to gravity.

In this case, the buoyant force is equal to the weight of the water displaced by the object, which is also known as the apparent weight. So, to find the apparent weight, you will need to rearrange the equation to solve for V.

V = (W - Fb)/(ρg)

Substituting the values given in the problem, we get:

V = (0.442N - 0.037N)/(1000kg/m^3)(9.8m/s^2)

V = 0.405m^3

Therefore, the volume of the object is 0.405m^3. This means that when the object is submerged in water, the apparent weight is equal to the weight of the water displaced, which is 0.405m^3 x 1000kg/m^3 x 9.8m/s^2 = 3.96N.

To summarize, to find the apparent weight when submerged in water, you need to use the buoyant force equation and solve for V. Then, you can calculate the apparent weight by multiplying the volume by the density of the fluid and the acceleration due to gravity.
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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