By how much is each post compressed?

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SUMMARY

The discussion centers on calculating the compression of wood posts supporting a 30,000 L aquarium. Each post has a square cross-section of 6.00 cm x 6.00 cm and a height of 90.0 cm, with Young's modulus (Y) for wood set at 1010 N/m2. The total weight of the water is calculated as 294,000 N, leading to a compression (ΔL) of 0.00184 m. The final answer required three significant figures, which was a key factor in determining correctness.

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Wimpalot
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Homework Statement


A large 30000 L aquarium is supported by four wood posts at the corners. Each post has a square 6.00 cm x 6.00 cm cross section and is 90.0 cm tall. Take Y=10^10 for wood

Homework Equations


ΔL = FL/AY
F = ma
ρ = m/V

The Attempt at a Solution


So the total area is 0.06 * 0.06 * 4 = 0.0144m2
The length of each post is 0.9m
The total mass of water is 30000kg (taking the density as 1kg/L)
Meaning the weight is 30000*9.8 = 294000N
And Y=1010

Which gives:
ΔL = (294000*0.9)/(0.0144*1010
= 0.00184

But this is apparently wrong. I have no idea what I did wrong
 
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Were they expecting the answer to be given in particular units?
 
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It has never mattered before as I can specify the units. So it shouldn't matter.
 
Wimpalot said:
It has never mattered before as I can specify the units. So it shouldn't matter.
Well, I can't spot any other issues. Your calculations look okay to me. Unless of course this is a salt-water aquarium?
 
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gneill said:
Well, I can't spot any other issues. Your calculations look okay to me. Unless of course this is a salt-water aquarium?
That was my second thought. In which case I get 0.0019 which was also incorrect. So yeah, no idea what the issue is maybe they do want different units so I may try that otherwise I don't know. I only get 5 attempts (this is mastering physics)
 
Turns out every other question wants two significant figures except this one which wanted exactly 3 to be correct so yeah. 0.00184 was correct. Thanks for the assistance
 

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