What is the buoyant force of water on the block?

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SUMMARY

The buoyant force of water on the block is calculated by subtracting the weight of the block in water (20 N) from its weight in air (50 N), resulting in a buoyant force of 30 N. The discussion also touches on harmonic motion, where the total mechanical energy of a mass-spring system can be calculated using the formula E = 1/2 k a^2, where k is the spring constant (20 N/m) and a is the amplitude (0.2 m), yielding an energy of 0.4 J. The participants confirm the correctness of these calculations, emphasizing the simplicity and accuracy of the methods used.

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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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