Tuesday, April 20, 2010

Work (physics)

mechanical work is the amount of energy transferred by a force acting through a distance. Like energy, it is a scalar quantity, with SI units of joules. The term work was first coined in 1826 by the French mathematician Gaspard-Gustave Coriolis.[1][2]

According to the work-energy theorem if an external force acts upon a rigid object, causing its kinetic energy to change from Ek1 to Ek2, then the mechanical work (W) is given by:[3]

W = \Delta E_k = E_{k_2} - E_{k_1} = \tfrac12 m (v_2^2 - v_1^2) \,\!

where m is the mass of the object and v is the object's velocity.

If the resultant force F on an object acts while the object is displaced a distance d, and the force and displacement act parallel to each other, the mechanical work done on the object is the product of F multiplied by d:[4]

W = F \cdot d

If the force and the displacement are parallel and in the same direction, the mechanical work is


\mathbf{F} = \frac{\mathrm{d}}{\mathrm{d}t}(m \mathbf{v})
Newton's Second Law
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positive. If the force and the displacement are parallel but in opposite directions (i.e. antiparallel), the mechanical work is negative.

However, if the force and the displacement act perpendicular to each other, zero work is done by the force:[4]

W = 0\;
Posted by composemind at 12:41 AM

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