Physics 1029A/B Lecture Notes - Lecture 3: Buoyancy, Net Force

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maroonskunk233

15 Feb 2016

School

Western University

Department

Physics

Course

Physics 1029A/B

Professor

Martin Zinke- Allmang

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Document Summary

The of an isf (ideal stationary fluid) into which an object is realised has a profound effect on the resulting motion of an object. Archimedes" principle: when an object is immersed in a fluid, the fluid exerts an upward force on the object equal to the weight of the fluid displaced by the object . The net force is equal to the weight of the displaced fluid minus the weight of object. Note that wf has the same magnitude as the buoyant force: if fnet > 0, if fnet = 0. Then the weight of the object is less than the buoyant force, so the object floats to the surface. The object floats at its current depth below the fluid surface as the buoyant force = the weight of the object: if fnet < 0. The weight of the object is greater than the buoyant force and thus the object sinks to the bottom of the container.

Related Questions

Archimedes’ Principle states that the buoyant force on an object partially or fully submerged in a fluid is equal to the weight of the fluid that the object displaces. Thus, for an object of density ρ0ρ0 floating partly submerged in a fluid of density ρfρf, the buoyant force is given by

where g is the acceleration due to gravity and A(y) is the area of a typical cross-section of the object (see the figure). The weight of the object is given by

(a) Show that the percentage of the volume of the object above the surface of the liquid is .

(b) The density of ice is and the density of seawater is . What percentage of the volume of an iceberg is above water?

(d) A sphere of radius and having negligible weight is floating in a large freshwater lake. How much work is required to completely submerge the sphere? The density of the water is .

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where g is the acceleration due to gravity and A(y) is the area of a typical cross-section of the object (see the figure). The weight of the object is given by

(a) Show that the percentage of the volume of the object above the surface of the liquid is .

(b) The density of ice is and the density of seawater is . What percentage of the volume of an iceberg is above water?

(d) A sphere of radius and having negligible weight is floating in a large freshwater lake. How much work is required to completely submerge the sphere? The density of the water is .

$F = ρ_{f} g \int_{- h}^{0} A (y) d y$

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Archimedes’ Principle states that the buoyant force on an object partially or fully submerged in a fluid is equal to the weight of the fluid that the object displaces. Thus, for an object of density floating partly submerged in a fluid of density , the buoyant force is given by

where g is the acceleration due to gravity and A(y) is the area of a typical cross-section of the object (see the figure). The weight of the object is given by

(a) Show that the percentage of the volume of the object above the surface of the liquid is .

(b) The density of ice is and the density of seawater is . What percentage of the volume of an iceberg is above water?

(d) A sphere of radius and having negligible weight is floating in a large freshwater lake. How much work is required to completely submerge the sphere? The density of the water is .