Math Problem Statement
A tank has a shape of a cone with a radius at the top of 3 m and a height of 5 m. The tank also has a 1 m spout at the top of the tank. The tank is filled with water up to a height of 2 m. Find the work needed to pump all the water out the top of the spout. (Use 9.8 m/s2 for g and the fact that the density of water is 1000 kg/m3.)
Solution
We are tasked with finding the work required to pump water out of a conical tank with a spout. To solve this, we'll need to use the following concepts:
- Density of water:
- Gravitational acceleration:
- The formula for work done in moving a volume of liquid against gravity is: where is the force, and represents an infinitesimal change in height.
Step-by-step Plan:
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Volume Element: We'll first calculate the volume of an infinitesimal slice of water at a height above the bottom of the cone. Given the geometry of the cone, the radius of the water slice varies with height.
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Geometric Similarity: Since the tank is a cone, the radius at any height is proportional to the height from the tip of the cone. For this cone:
- At the top , the radius is .
- Using the similarity of triangles:
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Infinitesimal Volume : The infinitesimal volume of a slice of water at height with thickness is the volume of a cylinder with radius and height :
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Force to Lift Water: The weight of this infinitesimal volume of water is :
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Distance to Lift Water: To pump water out of the spout, the water at height needs to be lifted a distance of meters (since the spout is 1 meter above the top of the cone).
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Work for Infinitesimal Slice: The work to pump this infinitesimal slice is:
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Total Work: Integrate this expression from to , as the tank is filled to a height of 2 meters: Simplifying constants:
Step-by-step Integration:
Now, we'll evaluate the integral:
Let's calculate each part:
Thus, the total integral is:
Final Work Calculation:
Now substitute this result into the expression for : Approximating , we get:
Thus, the total work required to pump all the water out of the tank is approximately .
Would you like more details or have any questions?
Here are 5 related questions for further exploration:
- How would the work change if the height of the spout were increased to 2 meters?
- What is the effect of changing the cone's base radius on the work required?
- How would the work differ if the tank were only half-filled with water?
- What if the water density were lower, like for oil (850 kg/m³)?
- How does the shape of the tank (e.g., cylindrical vs. conical) affect the work required?
Tip: Always check the dimensions of your parameters to ensure consistency when solving physics-related problems!
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Math Problem Analysis
Mathematical Concepts
Calculus
Volume of Revolution
Work-Energy Principle
Formulas
W = ∫ F dy
dV = π(3/5 y)^2 dy
dF = 1000 × 9.8 × dV
Work = ∫ 35280π y^2 (6 - y) dy
Theorems
Geometric Similarity
Work-Energy Theorem
Suitable Grade Level
Undergraduate Physics or Calculus Level
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