How Much Does a Marble Column Compress Under Load?

[Jbreezy]

Homework Statement

A marble column with cross sectional area of 45cm^2 supports a load of 8.5 x 10^4 Newtons.
The marble has a Young's modulus of 5.5 x 10^10 N/m^2 and a compressive strength of 1.8 x 10^8 Pa. If the column is 2.75m high, what is the change in length of the column?

Homework Equations

Y(ΔL/L) = F/A

Where Y is young modulus.

The Attempt at a Solution

Y(ΔL/L) = F/A
Solve the equation for ΔL and you get.
ΔL = (FL)/ (AY)
So plugging in the values you get.
ΔL = ((8.5 x 10^4 N)(2.75m)) / ((.45m^2)(5.5 x 10^10 N/m^2))
So ΔL = 9.44 x 10^-6
Can someone double check me? I don't understand why my instructor gave me this number
1.8 x 10^8 Pa.
Please confirm or deny my answer. Thanks very much.

 

[mfb]

45cm^2 is not .45m^2.

Can someone double check me? I don't understand why my instructor gave me this number
1.8 x 10^8 Pa.

Maybe to check if the column breaks down.

 

[Jbreezy]

OK. So with that correction

ΔL = ((8.5 x 10^4 N)(2.75m)) / ((0.0045 m^2)(5.5 x 10^10 N/m^2))
So ΔL = 9.44 x 10^-4

Is this correct now? Thanks for the help.

 

[mfb]

Looks fine