Calculating the Kinetic Energy of a Package

Strategy

Because the mass $m$ and speed $v$ are given, the kinetic energy can be calculated from its definition as given in the equation $KE = \frac{1}{2} {mv}^{2}$ .

Solution

The kinetic energy is given by

KE = \frac{1}{2} {mv}^{2} .

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Entering known values gives

KE = 0 . 5 (30.0 kg) (0.500 m/s)^{2},

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which yields

KE = 3.75 kg \cdot m^{2} {/s}^{2} = 3.75 J.

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Discussion

Note that the unit of kinetic energy is the joule, the same as the unit of work, as mentioned when work was first defined. It is also interesting that, although this is a fairly massive package, its kinetic energy is not large at this relatively low speed. This fact is consistent with the observation that people can move packages like this without exhausting themselves.