Work problem, deals with great pyramid

  1. this is a calc problem, but I thought it fits better here than in the math section since its homework.

    Here it goes:

    the great pyramid of cheops is 410 feet tall and 755 feet square at the base. find the volume of the pyramid using calculus.

    Part two:
    The stone used in constructing it has a density of 200lb/ft^3. Find the work against gravity in building the pyramid.

    I understand you integrate from 0 to 410 of the volume of each slab with a thickness of deltaX(or would it be delta y?) I am unsure how to calculate part two though, i havent had much experience with work and force. anyone want to drop a hint or two :smile:
  2. jcsd
  3. StatusX

    StatusX 2,565
    Homework Helper

    You're right on the first part, and it doesn't matter what you call the integration variable. For the second part, the work done raising a mass m by a height h against a gravitational acceleration g is mgh. Add up the work done on each differential mass element ρdV, where ρ is the density.
  4. For each horizontal slice, its area, its volume, and its weight can all be expressed as functions of y (distance from the x-axis). And for each slice, the work done is equal to the weight times the height.
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