My activities as an Engineer often involve creative problem solving of the sort we did in last week’s blog when we explored the interplay between work and kinetic energy. We used the Work-Energy Theorem to mathematically relate the kinetic energy in a piece of ceramic to the work performed by the friction that’s produced when it skids across a concrete floor. A new formula was derived which enables us to calculate the kinetic energy contained within the piece at the start of its slide by means of the work of friction. We’ll crunch numbers today to determine that quantity.

The formula we derived last time and that we’ll be working with today is,

Calculating Kinetic Energy By Means of the Work of Friction

where, KE is the ceramic piece’s kinetic energy, F_{F} is the frictional force opposing its movement across the floor, and d is the distance it travels before friction between it and the less than glass-smooth floor brings it to a stop.

The numbers we’ll need to work the equation have been derived in previous blogs. We calculated the frictional force, F_{F,} acting against a ceramic piece weighing 0.09 kilograms to be 0.35 kilogram-meters/second^{2} and the measured distance, d, it travels across the floor to be equal to 2 meters. Plugging in these values, we derive the following working equation,

KE = 0.35 kilogram-meters/second^{2} × 2 meters

KE = 0.70 kilogram-meters^{2}/second^{2}

The kinetic energy contained within that broken bit of ceramic is just about what it takes to light a 1 watt flashlight bulb for almost one second!

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