2 - WorkPowerEnergy - Power

University:
High School
Course:
High School Physics
Academic year:

2024
Views:

245

Pages:

13
Author:

1 1

Unit 5: Work, Power and Energy Power 5.2: Power Is the rate at which work is done ◼ A machine that does a certain amount of work the fastest develops the most power ◼ Unit: ◼  Watt (W) W P= t work time Ex #1 What is the power of a bulldozer that does 5.5 x 104J of work in 1.1s? W P= t 5.5 • 10 P= 1.1 P = 5.0 • 10 W 4 4 Ex #2 How much power is developed by a 60.0kg boy running up a 4.5m high flight of stairs in 4.0s? W P= t Fd P= t (60)(9.8)(4.5) P= 4 mgd P= t P = 6.6 • 10 W 2 Ex #3 A boy who can generate 500.0W runs up a flight of stairs in 5.0s. How high are the stairs if the boy has a mass of 62kg? W P= t Fd P= t (62)(9.8)(?) 500 = 5 mgd P= t d = 4.1m Ex #4 An elevator motor can produce 2200W of power. The elevator has a mass of 1100kg. Ignoring air resistance & friction, at what constant speed will the elevator rise? Fd P= t mgd P= t 2200 = (1100)(9.8)(v) v = 0.20m / s W P= t v Ex #5 A 1500.0 kg car accelerates uniformly from rest to a speed of 27.78 m/s in 10.0 s. What power is required to produce this motion? (ignore friction) W P= t need Fd P= t v2 = v1 + at and mad P= t 1 2 d = v1t + at 2 v2 = v1 + at P= 27.78 = 0 + a (10) a = 2.78m / s 2 Fapp d t mad P= t (1500)(2.78)(138.89) P= 10 P = 5.79 • 10 W 4 1 2 d = v1t + at 2 1 d = (0)(10) + (2.78)(10) 2 2 d = 138.89m Ex #6 A winch moves a 200.0kg air conditioner to the roof of a building 10.0 m high. It moves along a frictionless ramp of angle 14.0° at constant speed of 2.00 m/s. v=2m/s 200kg 10m What is the power of the winch? Find t: Ex #7 A car with a total mass of 1200.0 kg drives up a 12° incline. 12o How much power does the motor produce to move the car 1000.0m at a constant speed of 25.0m/s while experiencing a coefficient of friction of 0.250? Two downhill forces; friction and weight! Find Fapp: Find P: Find t: Quantum: HW: pg 334 #1, 2, 4, 5 & 8