Chapter 5 - Work

# Chapter 5 - Work - Chapter 5: Work & Energy Start ! CHAPTER...

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PPH0015 Prepared by Thumaun Start ! CHAPTER 5 Work & Energy

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PPH0015 Prepared by Thumaun Overview : 1. 1. Work done by constant force 2. Work done by varying force 3. Energy - Kinetic energy 4. Energy - Potential energy 5. Work done by spring 1. The Work-Energy Theorem 2. Principle of Conservation of Energy 3. Power 4. Efficiency Chapter 5: Work & Energy
PPH0015 Prepared by Thumaun Kinematics Dynamic Mechanics - the description of how objects move -physical quantities are x , v , a and t - deals with force and why objects move -physical quantities are F (Force) the link is ‘a’ 2 m kx 2 1 U energy, potential s Spring' = mgh U energy, potential nal Gravitatio = 2 mv 2 1 K energy, Kinetics = ( 29 θ cos x F F.x W done, Work = =

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PPH0015 Prepared by Thumaun Definitions WORK : Work is done by a force acting on an object when the point of application of that force moves through some distance and the force has a component along the line of motion . The symbol is W . The unit is Newton Meter ( Nm ) or Joule ( J )
PPH0015 Prepared by Thumaun Definitions ENERGY : The ability to do work. KINETIC ENERGY : Energy associated with the motion of an object The symbol is K . The unit is J POTENTIAL ENERGY : Energy associated with the position or configuration of an object Example : Gravitational potential energy (U = mgh) & Elastic (spring) potential energy ( U = ). The symbol is U and the unit is J . 2 2 1 m kx

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PPH0015 Prepared by Thumaun Work done by Constant Force: The work W done by an agent exerting a constant force is the product of the component of the force in the direction of the displacement and the magnitude of the displacement of the force W = F s cos θ = F . s
PPH0015 Prepared by Thumaun Work done by Constant Force: 1) A force does no work on a particle if the particle does not move . If s = 0, W = Fs cos θ = 0 2) The work done by a force is zero when the force is perpendicular to the displacement. If F s , then θ = 90 0 , W = Fs cos θ = Fs cos 90 0 = 0 3) The work done W = F s when the applied force F acts along the direction of the displacement. If θ = 0, W = Fs cos 0 = F s 4) The work done W = - F s when the applied force F acts in the opposite direction of the displacement. If θ = 180 , W = Fs cos 180 = - F s

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PPH0015 Prepared by Thumaun Work done by Constant Force: For the above diagram : W n = n s cos 90 0 = 0 W F = F s cos θ
PPH0015 Prepared by Thumaun Work done by Constant Force: The sign of the W depends on the

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## This note was uploaded on 10/04/2008 for the course PYHSICIS 191 taught by Professor Bradly during the Spring '08 term at Abilene Christian University.

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Chapter 5 - Work - Chapter 5: Work & Energy Start ! CHAPTER...

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