A 20. kg suitcase at the baggage handling facility of an airport has an initial

Question

A 20. kg suitcase at the baggage handling facility of an airport has an initial speed of 8.0 m/s and slides to rest due to friction on a flat, horizontal surface. The coefficient of kinetic friction for the suitcase on the surface is 0.20. Use the following two methods to calculate the average power produced by friction as the suitcase comes to rest: (a) Use Newton’s 2nd Law to find the acceleration, use constant acceleration equations to find x and t, then calculate the work done by friction and finally the power. (b) Use the work-energy theorem to find the work (from the change in kinetic energy), and then find the power (using the t found in part (a)). Be sure to include the proper sign on the work done by friction.

Explanation / Answer

By Newton 2nd law

Net force=0.2*mg=39.2 N

a=net force/mase=1.96 m/s(2)

Displacement=16.33 m

Time=4.08 sec

Work done by friction=-friction force*displacement=-640J

Power=156.8 W

Using work energy theorem

Initial energy=energy lost in friction as final energy is zero So

Energy lost in friction=0.5*m*v*v=640 J

Work done by friction=-640 J

Power=156.8 W

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