1 - WorkPowerEnergy - Work | High School

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High School
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High School Physics
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2024
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Unit 5: Work, Power and Energy Intro to Work 5.1: Work: An applied force acting over a displacement ◼ Force & motion must be in the same direction ◼ Applied force must cause motion for work to be done ◼ Work is measured in J (Joules) & is a scalar ◼ W = Fd J m N ◼ Ex.  Pushing against a wall = NO work ◼ Ex.  Pushing against a wall = NO work  Carrying books while walking = NO work on books  Lifting your backpack from the floor = WORK  Going up stairs = WORK Ex #1 How much work is done by a boy pushing a car with a force of 800.0 N for a distance of 200.0 m? F = 800.0 N d = 200.0 m W=? W = Fd W = (800.0)( 200.0) 5 W = 1.600 • 10 J Ex #2 A camper uses a rope to raise a pail of water (mass 20.0kg) 3.50m upward from a well. How much work is done by the camper? F=? d = 3.50m W=? F = mg W = Fd F = (20)(9.8) W = (196)(3.5) F = 196N Ex #3 A boy pulls a sled 30.0m with a rope, angled 20.0̊ from the ground. The force in the rope is 300.0 N. How much work is done by the boy? 300.0 N Δd = 30.0 m H O 20.0o ? ? cos 20 = 300 0 A F = 281.91N W = Fd W = (281.91)(30) W = 8.46 • 10 J 3 Ex #4 A 1000.0kg car accelerates uniformly from rest to a speed of 20.0m/s in 16.0s. How much work is done by the engine during this time? v2 = v1 + at 20 = 0 + a (16) a = 1.25m / s 2 Fnet = ma 1 2 d = v1t + at 2 1 d = (0)(16) + (1.25)(16) 2 2 d = 160m F = (1000)(1.25) Fapp = 1250 N ( Ff = 0) W = Fd W = (1250)(160) W = 2.00 • 10 J 5 Ex #4 A 1000.0kg car accelerates uniformly from rest to a speed of 30.0m/s in 12.0s. How much work is done by the engine during this time? Ff=750.0N. Ex #5 Force is exerted on an object to displace it. How much work is done to displace the object 10m? W = Fd 10 Force (N) 8 Area under curve = work 6 4 2 0 0 2 4 6 Displacement (m) 8 10 12 71J Quantum: HW: pg 330 #1-5