PHY 107 1st Edition Lecture 15 Outline of Last Lecture I. Work (cont.)Outline of Current LectureII. Work-Kinetic Energy TheoremIII. PowerCurrent LectureWork-Kinetic Energy Theorem:- Kf – Ki = Wnet and ∆K = Kf – Ki so ∆K = Kf – Ki = Wnet↓ Change in kinetic energy of a particle = work done on a particle- If Wnet > 0 (0 < θ < 90°) → Kf – Ki > 0 → Kf > Ki- If Wnet < 0 (90° < θ < 180°) → Kf – Ki < 0 → Kf < KiWith variable force:- Variable force F(x) moves an object of mass m from point A(x = xi) to point B(x = xf)- Exact same form as in the case when F is constant Wnet = Kf – Ki = ∆KPower:- Power: P – the rate at which work is done by a force F- If F does work Win a time interval ∆t, Pavg = w∆ tThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Instantaneous power: P = dWdt- Units of P:o Watt, W: W = 1 J/1 so 1 hp (horsepower) = 746 Wo Kilowatt-hour, kWh: work performed by an engine of power P = 1000 W in a time interval of 1 hour o W = Pt = 1000 x 3600 = 3.60 x 106 J - Consider a force F acting on a particle at an angle of θ to the motion; the rate at which F does work is:o P = dWdt = Fcos θ dxdt = Fcosθdxdt = Fvcosθo P = Fvcosθ = ´F ·
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