Math Problem Statement

Calculate the fluid force on one side of a semicircular plate of radius 8 ft that rests vertically on its diameter at the bottom of a pool filled with water to a depth of 12 ft. Assume the weight-density of water is 62.4 lb/ft^3.

Solution

To solve the problem in the image, where you are tasked with calculating the fluid force on one side of a semicircular plate, we will use principles from fluid mechanics. Here's a step-by-step approach:

Information provided:

  • Radius of the plate, r=8ftr = 8 \, \text{ft} (semicircular plate).
  • Water depth, h=12fth = 12 \, \text{ft}.
  • Weight-density of water, ρ=62.4lb/ft3\rho = 62.4 \, \text{lb/ft}^3.

The fluid force on the plate is determined by integrating the pressure at different depths. The pressure PP at a depth yy below the surface of the water is:

P(y)=ρyP(y) = \rho \cdot y

Steps:

  1. Find the depth yy for each horizontal strip of the semicircular plate and calculate the pressure acting at that depth. The plate is located vertically, so the pressure varies along its height.

  2. Break the semicircular plate into differential horizontal strips at different depths below the water surface and calculate the force on each strip.

    The fluid force on a small strip of area dAdA is given by: dF=P(y)dA=ρydAdF = P(y) \cdot dA = \rho \cdot y \cdot dA

    For a semicircular plate of radius rr, the differential area dAdA for a horizontal strip is the width of the strip times the thickness dydy, which is: dA=2r2x2dydA = 2 \cdot \sqrt{r^2 - x^2} \cdot dy where xx is the distance from the center of the plate.

  3. Set up the integral over the height of the plate. The total force FF is: F=0rρy2r2y2dyF = \int_{0}^{r} \rho \cdot y \cdot 2 \cdot \sqrt{r^2 - y^2} \, dy

  4. Integrate to find the total force.

I will now compute the total fluid force using these steps.The total fluid force on one side of the semicircular plate is approximately 21,299.2 lb.

Would you like further details or have any questions about the process?

Here are 5 follow-up questions to explore:

  1. How would the fluid force change if the water depth was increased?
  2. What happens to the fluid force if the plate is fully submerged?
  3. How would you calculate the fluid force if the plate was rectangular instead of semicircular?
  4. How does the shape of the object affect the distribution of fluid pressure?
  5. How would the result differ if the plate was oriented horizontally instead of vertically?

Tip: When working with fluid mechanics problems, always ensure that the units of density and area are consistent for proper force calculation.

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Math Problem Analysis

Mathematical Concepts

Fluid Mechanics
Integration
Pressure Calculation

Formulas

Pressure at depth y: P(y) = ρ * y
Differential Force: dF = ρ * y * dA
Area of a strip on the semicircular plate: dA = 2 * sqrt(r^2 - y^2) * dy
Total Force: F = ∫(ρ * y * 2 * sqrt(r^2 - y^2)) dy

Theorems

Pressure-Depth Relationship
Integration of Force over Area

Suitable Grade Level

College-level (Fluid Mechanics, Calculus)