Where θ is the angle that separates the vectors. The second form of the equation is the expanded form of the "dot product" in the first equation. In physics, the dot product "a · b" (read "a dot b") can be rewritten as "a b cos θ".
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When the force is not constant, the correct expression uses [[integration]]:
Work is a transfer of [[energy]]; if ''W'' is positive, there is a transfer of energy ''to'' the system, and if ''W'' is negative there is a transfer of energy ''from'' the system.
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Its units are that of force multiplied by distance, in SI this is [[newton (unit)|Newton]] · [[Meter]], or [[Joule]]. The aberrant unit kWh (kilowatt-hour) is sometimes used; this unit is the product of kilowatt, or 1,000 Watts (Joules per second), and hour, or 3,600 seconds.