## 1-27-14 OT

 Work A baseball pitcher does positive work on the ball by applying a force to it over the distance it moves while in his grip. Common symbol(s): W in SI base quantities: 1 kg·m2/s2 SI unit: joule (J) Derivations from other quantities: W = F · dW = τ θ

In physics, a force is said to do work when it acts on a body, and there is a displacement of the point of application in the direction of the force. The force does not need to cause the displacement. For example, when you lift a suitcase from the floor, there are two forces that do work: the normal force by your hand and the gravitational force.

The term work was introduced in 1826 by the French mathematician Gaspard-Gustave Coriolis[1][2] as "weight lifted through a height", which is based on the use of early steam engines to lift buckets of water out of flooded ore mines. The SI unit of work is the newton-metre or joule (J).

The work done by a constant force of magnitude F on a point that moves a displacement (NOT distance) d in the direction of the force is the product,

$W = Fd.$

For example, if a force of 10 newtons (F = 10 N) acts along a point that travels 2 metres (d = 2 m), then it does the work W = (10 N)(2 m) = 20 N m = 20 J. This is approximately the work done lifting a 1 kg weight from ground to over a person's head against the force of gravity. Notice that the work is doubled either by lifting twice the weight the same distance or by lifting the same weight twice the distance.

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