A wooden block of width 2m, depth 1.5m and length 4m floats horizontally in water. Find the volume of water displaced and the position of center of buoyancy. The specific gravity of wooden block is 0.7.

Floating Wooden Block Analysis

Problem Statement

A wooden block of dimensions:

  • Width: 2m
  • Depth: 1.5m
  • Length: 4m
  • Specific gravity: 0.7

The block floats horizontally in water. Determine:

  1. The volume of water displaced.
  2. The position of the center of buoyancy.

Solution

1. Calculate Volume of Water Displaced

Using the principle of buoyancy: \[ \gamma_{\text{wood}} V_{\text{wood}} = \gamma_{\text{water}} V_{\text{displaced water}} \] \[ (0.7 \times 9810 \times 2 \times 1.5 \times 4) = 9810 \times V_{\text{water displaced}} \] \[ V_{\text{water displaced}} = 8.4 \text{ m}^3 \]

2. Calculate Depth of Immersion (\( h \))

Since the weight of the block equals the weight of the displaced water: \[ \gamma_{\text{wood}} V_{\text{wood}} = \gamma_{\text{water}} V_{\text{displaced water}} \] \[ 0.7 \times 9810 \times 2 \times 1.5 \times 4 = 9810 \times 2 \times 4 \times h \] \[ h = 1.05 \text{ m} \]

3. Position of Center of Buoyancy

The center of buoyancy is at the centroid of the submerged volume: \[ \text{Position of center of buoyancy} = \frac{h}{2} = \frac{1.05}{2} \] \[ = 0.525 \text{ m from the bottom} \]
Final Results:
  • Volume of water displaced: 8.4 m³
  • Position of center of buoyancy: 0.525 m from the bottom

Explanation

1. Buoyancy Principle:
A floating body displaces a volume of liquid equal to its weight. Since the block is in equilibrium, the weight of the block is equal to the weight of the displaced water.

2. Depth of Immersion Calculation:
The total volume of the wooden block is known, and since it has a specific gravity of 0.7, only 70% of its volume needs to be submerged to balance the weight.

3. Center of Buoyancy:
The center of buoyancy is the centroid of the submerged portion of the block. Since the block is uniformly submerged, the center of buoyancy lies at half the submerged depth.

Physical Meaning

1. Floating Stability:
The position of the center of buoyancy plays a crucial role in determining the stability of a floating body. If the center of gravity is above the center of buoyancy, the body may tip over.

2. Archimedes’ Principle in Application:
This principle governs how ships and floating objects remain stable in water. Engineers use similar calculations to design floating structures, boats, and ships.

3. Use in Marine Engineering:
Ships are designed so that their center of buoyancy shifts with loading conditions, ensuring stability under different weights.

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top