Math Problem Statement

A conical​ container, oriented such that its vertex is at the​ bottom, has radius 8 ft and height 32 ft. It is filled to a height of 30 ft of a liquid weighing 62.4 lb divided by ft cubed. How much work will it take to pump the contents to the​ rim? How much work will it take to pump the liquid to a level of 2 ft above the​ cone's rim? not rounded

Solution

Given Information:

  • The container is a cone with:
    • Radius (R) = 8 ft
    • Height (H) = 32 ft
  • The liquid is filled to a height of 30 ft.
  • The weight density of the liquid is 62.4 lb/ft³.
  • We need to find the work to:
    1. Pump the liquid to the rim of the cone.
    2. Pump the liquid to a level 2 ft above the cone's rim.

Work to Pump Liquid to the Rim:

  1. Volume element at height yy:

    The cone is similar at any horizontal cross-section. The radius of the cone at any height yy is proportional to yy, so we use similar triangles:

    r(y)=832y=y4r(y) = \frac{8}{32} y = \frac{y}{4}

    The area of a cross-section at height yy is:

    A(y)=πr(y)2=π(y4)2=πy216A(y) = \pi r(y)^2 = \pi \left( \frac{y}{4} \right)^2 = \frac{\pi y^2}{16}

  2. Volume of a thin slice of liquid at height yy with thickness dydy is:

    dV=A(y)dy=πy216dydV = A(y) dy = \frac{\pi y^2}{16} dy

  3. Mass of the slice (since mass = density × volume):

    dM=ρdV=62.4πy216dydM = \rho dV = 62.4 \cdot \frac{\pi y^2}{16} dy

  4. Work to pump the liquid at height yy to the rim (height = 32 ft):

    The work to pump this slice is the weight of the slice times the distance it needs to be moved (32 − y):

    dW=(62.4πy216)(32y)dydW = \left( 62.4 \cdot \frac{\pi y^2}{16} \right) \cdot (32 - y) dy

  5. Total work to pump the liquid to the rim (integrating from y=0y = 0 to y=30y = 30):

    W=03062.4πy216(32y)dyW = \int_0^{30} 62.4 \cdot \frac{\pi y^2}{16} \cdot (32 - y) \, dy

Work to Pump Liquid 2 ft Above the Rim:

To pump the liquid to 34 ft (2 ft above the rim), the only difference is the distance to pump the liquid, which is now 34y34 - y.

  1. Total work to pump the liquid to 34 ft:

    Wabove=03062.4πy216(34y)dyW_{\text{above}} = \int_0^{30} 62.4 \cdot \frac{\pi y^2}{16} \cdot (34 - y) \, dy

I'll now compute both integrals to get the exact values.The exact work required to pump the liquid:

  1. To the rim of the cone (32 ft) is 333450π333450 \pi ft-lb.
  2. To 2 ft above the rim (34 ft) is 403650π403650 \pi ft-lb.

If you prefer, I can also express these values numerically.

Would you like to see more details, or do you have any questions?

Here are some related questions for further exploration:

  1. How does the shape of the container affect the work needed to pump the liquid?
  2. What would the work be if the liquid was filled to a different height?
  3. How would the work change if the cone had a different radius or height?
  4. How does the weight density of the liquid influence the work done?
  5. How does pumping the liquid to different heights above the cone impact the work required?

Tip: For objects with varying cross-sections like cones, the work calculation requires integrating both volume and distance.

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Math Problem Analysis

Mathematical Concepts

Calculus
Work and Energy
Integration
Geometry of Solids

Formulas

r(y) = (y/4)
Area of cross-section: A(y) = (πy^2)/16
Work formula: dW = (62.4πy^2/16) × (32 - y) dy
Total Work: W = ∫₀³⁰ (62.4πy^2/16) × (32 - y) dy

Theorems

Work-Energy Theorem
Volume Integration for Solids of Revolution

Suitable Grade Level

College Level - Calculus II or III