PHY 317K 1st Edition Lecture 7Outline of Last LectureI. WorkII. Conservation of EnergyOutline of Current LectureI. Work at an angleII. Potential EnergyIII. Kinetic EnergyCurrent LectureWork:- Work is equal to force times distance- Work done at an angle is equal to:1. A block moves to the right in the positive x-direction through the displacement delta X while under the influence of a force with the same magnitude F. Which is the correct order o the amount of work done by the force F, from the most positive to the most negative?Answer: C, A, D, BConservation of Energy:There are two types of energy:- Potential Energyo Position of the object in a force fieldo PE = mgh- Kinetic Energyo KE = ½ mv^2o Depends on the motion or speed of an object- Non-Conservative Force: Work depends on the path when friction is involved (friction can be air resistance or anything that is an opposing force)- Conservative Force: Work does NOT depend on the path, so regardless of the path that the object takes, the work is the sameo KEi + PEi = KEf + PEf o The summation of the initial kinetic and potential energy is equal to the final kinetic and potential energy1. A driver of mass m drops from a diving board above 10 m the water surface. Neglect air resistance.(a) Use conservation of energy to find his speed 5 m above the water’s surface.Answer: KEi + PEi = KEf + PEf KEi = 0 so…Mgh = ½ mv^2 + mgh (cancel the mass from both sides and plug in answers)9.8 (10) = ½ v^2 + 9.5(5)v = 9.899 m/s(b) Find his speed as he hits the water.Answer:Mgh = ½ mv^2 since the initial kinetic energy equals 0 and the final potential energy equals 0.Mgh = ½ mv^2 (plug in numbers and cancel mass from both sides)9.8 (10) = ½v^2v = 14
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