1. Power Chapter 5, Section 4

2. Power Power is the rate at which energy is transferred. Ex. The rate at which a light bulb transfers energy depends on its wattage.

3. P = W/Δt P = Fd/Δt P = Fν P = maν Mathematically expressed as: Power can be measured in either watts (W) or in horsepower (hp). 1 hp = 746 watts 1 W = 1 J/s

4. Sample Problem A 193 kg curtain needs to be raised 7.5 m at a constant speed in as close to as 5.0 s as possible. Which of the following motors is the best for the job: 1.5 kW, 3.5 kW, or the 5.5 kW motor. m = 193 kgΔt = 5.0 sd = 7.5 m P = W/Δt= Fd/Δt= mad/Δt P = (193 kg) (9.81 m/s²) (7.5 m) / 5.0 s g = 9.81 m/s² P ≈ 2.8 x 10³ W or 2.8 kW