Lecture 5 - Work and Energy .pdf - Institute of...

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Institute of Mathematical Sciences and Physics University of the Philippines Los Baños PHYSICS3 Lecture 1 st SEM AY 2016-2017 |UPLB |ALBIA J.R. Lecture 5: Work and Energy
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PHYSICS3 Lecture 1 st SEM AY 2016-2017 |UPLB |ALBIA J.R. Learning Objectives At the end of this chapter, you should be able to: 1. Define Energy, Work, and Power; 2. Apply the Work-Kinetic Energy Theorem 3. Apply the Law of Conservation of mechanical Energy 4. Relate Newton’s Laws and the Conservation of Mechanical Energy by solving dynamics problems. 2
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PHYSICS3 Lecture 1 st SEM AY 2016-2017 |UPLB |ALBIA J.R. 3 1. Energy A quantifiableattributeof a physical system Not an object nor any substance Defined as the amount of work one system CAN do on another .
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PHYSICS3 Lecture 1 st SEM AY 2016-2017 |UPLB |ALBIA J.R. 4 1. Energy Physical Properties: Dimensions: ML 2 /T 2 Mass times (Length* Length) Over (Time *Time) Type: Derived, Scalar SI UNIT: Joule (abbr., J) Symbols: E, and many other depending on type.
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PHYSICS3 Lecture 1 st SEM AY 2016-2017 |UPLB |ALBIA J.R. 5 2. Work Energy is defined as the ability of a system to do work . Mechanical work is the amount of energy transferred by a force .
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PHYSICS3 Lecture 1 st SEM AY 2016-2017 |UPLB |ALBIA J.R. 6 2. Work Positive and negative signs of work indicate whether the object exerting the force is transferring energy to some other object, or receiving it. Positive sign is assigned to work, if it is done on the system . Negative sign is assigned to work, if the system does it on another system .
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PHYSICS3 Lecture 1 st SEM AY 2016-2017 |UPLB |ALBIA J.R. 7 2. What Exactly is work then? Physical Properties: Dimensions: ML 2 /T 2 Mass times (Length* Length) Over (Time *Time) Type: Derived, Scalar SI UNIT: Joule (abbr., J) Symbols: W
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PHYSICS3 Lecture 1 st SEM AY 2016-2017 |UPLB |ALBIA J.R. 8 2. Work: Unit Analysis W = Force*displacement [J]= [N] * [m] 1Joule = 1 Newton-meter
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PHYSICS3 Lecture 1 st SEM AY 2016-2017 |UPLB |ALBIA J.R. 9 2. Work done by a Constant Force The work W done by a constant force F whose point of application moves through a displacement d is defined to be W = F d = F d cos θ θ is the angle between F and the d axis d is the displacementcaused by the force
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PHYSICS3 Lecture 1 st SEM AY 2016-2017 |UPLB |ALBIA J.R. 10 Work is positive when the force has a component in the same direction with the displacement
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PHYSICS3 Lecture 1 st SEM AY 2016-2017 |UPLB |ALBIA J.R. 11 Work is negative when the force has a component opposite to the displacement
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PHYSICS3 Lecture 1 st SEM AY 2016-2017 |UPLB |ALBIA J.R. 12 Work is zero when the force is perpendicular to the displacement
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PHYSICS3 Lecture 1 st SEM AY 2016-2017 |UPLB |ALBIA J.R. 13 2. Work: Example A force of 12 N is exerted on a box at an angle of θ =40 o as in the figure below. How much work is done by the force as the box moves along the table a distance of 3m ?
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PHYSICS3 Lecture 1 st SEM AY 2016-2017 |UPLB |ALBIA J.R.
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