Defining Power

  • Power is the rate at which work is done

  • Power is the rate at which a force does work

  • Units of power are joules/second, or watts

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2003 Free Response Question 1

100 kg Mech. 1. The 100 kg box shown above is being pulled along the x-axis by a student. The box slides across a rough surface, and its position x varies with time t according to the equation x = 0.5t3 + 2t, where x is in meters and t is in seconds. (a) Determine the speed of the box at time t = O. (b) Determine the following as functions of time t. i. The kinetic energy of the box ii. The net force acting on the box iii. The power being delivered to the box (c) Calculate the net work done on the box in the interval t = O to t = 2 s. (d) Indicate below whether the work done on the box by the student in the interval t = O to t = 2 s would be greater than, less than, or equal to the answer in part (c). Greater than Justify your answer. Less than Equal to

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