Submitted by: Submitted by Colx
Views: 47
Words: 725
Pages: 3
Category: Science and Technology
Date Submitted: 09/13/2014 09:12 PM
Buoyancy
Archimedes’s 1st laws of buoyancy: A body immersed in a fluid experiences a vertical buoyant force equal to the weight of the fluid it displaces, see Fig. 9 and 10.
Fig. 9: an immersed body in a fluid, experiences a force equal to the weight of the fluid it displaces. The line of action of the buoyant force passes through the center of volume of the displaced body; i.e., the center of mass is computed as if it had uniform density. The point which FB acts is called the center of buoyancy. Both liquids and gases exert buoyancy force on immersed bodies.
Fig.10: Archimedes first law of buoyancy.
This equation assumes that the body has a uniform specific weight. A floating body displaces its own weight in the fluid in which it floats. In the case of a floating body, only a portion of the body is submerged, thus: weight of the floating body
M. Bahrami
Fluid Mechanics (S 09)
Fluid statics 9
Fig. 11: Archimedes second law of buoyancy. Example: Buoyancy force on a submerged object
A spherical body has a diameter of 1.5 m, weighs 8.5 kN, and is anchored to the sea floor with a cable as is shown in the figure. Calculate the tension of the cable when the body is completely immersed, 10.1 / . assume Solution: The buoyancy force FB is shown in the free‐body‐diagram where W is the weight of the body and T is the cable tension. For equilibrium, we have: The buoyancy force is; . And the volume of the body is:
6 The cable tension then becomes: 10.1 10 ⁄ 1.5 6
8.50
10
9.35
Seawater d
FB W T
Cable
M. Bahrami
Fluid Mechanics (S 09)
Fluid statics 10
Pressure distribution in rigidbody motion
Fluids move in rigid‐body motion only when restrained by confining walls. In rigid‐body motion, all particles are in combined translation and rotation, and there is no relative ...