What is the buoyant force of water on the block?

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Homework Help Overview

The discussion involves two distinct problems: one related to buoyant force in fluid mechanics and the other concerning total mechanical energy in harmonic motion. The first problem presents a block's weight in air and water, prompting questions about buoyancy, while the second problem involves a mass-spring system in oscillation.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • Participants explore the concept of buoyant force by comparing the weights of the block in air and water, with one suggesting a simple subtraction of the two weights. The second problem raises questions about calculating total mechanical energy, with some participants attempting to apply relevant formulas.

Discussion Status

Some participants have provided insights into the buoyant force calculation, indicating that the approach of subtracting the weights is valid. The second problem has seen attempts at calculating energy, with one participant confirming their calculation while another expresses uncertainty about the mass involved.

Contextual Notes

The first problem lacks information about the material's density, which may affect the understanding of buoyancy. The second problem does not specify the mass attached to the spring, which is crucial for a complete analysis of the mechanical energy.

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Homework Statement


A block of unknown material weighs 50 N in air and 20 N in water. What is the buoyant force of water?

Homework Equations


I know how to calculate density etc. I thought the formula to use was -density x V x g but it's not correct.


Homework Statement


A x Kg mass is attached to a horizontal spring of constant 20 N/m and set into harmonic motion with an amplitude = 0.2m. What is the total mechanical ernergy of the system?

I have no idea what to do... Some help would be greatly appreciated. Thanks!
 
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I was thinking it would be 50 - 20 = 30 but it seems a bit too simple to be true...
 
So for the second:
0.5 * 25 * 0.2^2 = 0.50J ?

THANK YOU!
 
It's simple and it's true.

I can't check your second answer because I can't see what the mass is.

[edit] E = 1/2ka^2 - whoops, you don't need the mass, so you're right there also.
 
Last edited:

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