Life jackets enable you float without the expenditure of energy. When properly worn, life jackets can prevent drowning in even an unconscious person. In 2005, of the 491 drowning deaths reported by the United States Coast Guard, 426 were not wearing a personal flotation device.
Buoyancy of Life Jackets
Life jackets work by changing the buoyant force of the person wearing the life jacket. The life jacket displaces a greater volume of water (increasing the buoyant force) without substantially increasing the mass (which would increase gravitational force), resulting in an upward buoyant force greater than the downward gravitational force.
The force of gravity is continually acting on an object. This downward force causes an object to sink in a fluid until an equivalent upward force is applied. Gravitational force is dependent on the mass of two objects--the person and the Earth.
Buoyancy is the upward force on an object partially or completely submerged in a fluid. The buoyant force is equal to the volume of fluid displaced.
If the buoyant force is greater than the force of gravity on an object, then it floats.
If the buoyant force is less than the force of gravity on an object, then it sinks.
Article Written By David Chandler
David Chandler has been a freelance writer since 2006 whose work has appeared in various print and online publications. A former reconnaissance Marine, he is an active hiker, diver, kayaker, sailor and angler. He has traveled extensively and holds a bachelor's degree from the University of South Florida where he was educated in international studies and microbiology.