# Calculating Work Help

• Sep 17th 2011, 10:42 AM
kevinnwhat
Calculating Work Help
Hi all, ive ran into a problem with this question, it reads,

calculate the work against gravity required to build the structure out of brick using the method of examples 2 and 3. Assume that brick has density 80lb/ft^3

A tower of height 20ft and square base of side 10ft.

I tried to figure out the work on one small layer, than take the integral from 0 to 20. So i first calculated the volume of each layer which i got 100*delta y, than i got the mass which is 8000, than i calculated the work (9.8)(8000)*delta y i than got F = 78400 delta y. So i tried to integrate that from 0 to 20 but i keep getting the wrong answer, anyone help me out here?
• Sep 17th 2011, 12:45 PM
skeeter
Re: Calculating Work Help
Quote:

Originally Posted by kevinnwhat
Hi all, ive ran into a problem with this question, it reads,

calculate the work against gravity required to build the structure out of brick using the method of examples 2 and 3. Assume that brick has density 80lb/ft^3

A tower of height 20ft and square base of side 10ft.

I tried to figure out the work on one small layer, than take the integral from 0 to 20. So i first calculated the volume of each layer which i got 100*delta y, than i got the mass which is 8000, than i calculated the work (9.8)(8000)*delta y i than got F = 78400 delta y. So i tried to integrate that from 0 to 20 but i keep getting the wrong answer, anyone help me out here?

what structure? how is it constructed? do you have a picture we can't see?

one more thing ... you won't be using the value 9.8. you've been given the weight-density of the brick in lbs/ft^3 (English units, not metric) , not the mass density.