# lecture19 - Work and Kinetic Energy Work by a variable...

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Work and Kinetic Energy Work by a variable force Kinetic Energy and the Work-Energy Theorem Serway & Jewett 7.3, 7.4

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Example (massless pulleys, no friction) s = 2 m How much work is done on the rope by F p ? = (25N)(2m) How much work is done by the upward force on the ball? = (100N)(0.5m) 100 N F P
Determine the work done by a force as the particle moves from x=0 to x=6m: x(m) F(N) 0 1 2 3 4 5 6 5

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Then the Work-Energy Theorem says: The total work done by all external forces acting on a particle is equal to the increase in its kinetic energy. Kinetic Energy Definition: for a particle moving with speed v, the kinetic energy is K = ½ mv 2 (a SCALAR) Proof: from Newton’s Second Law, and the definition of Work.
Kinetic Energy is measured in joules (1J=1Nm). Kinetic energy is a scalar; the work-energy theorem is a scalar relation. This theorem is equivalent to Newton’s Second Law. In principle, either method can be used for any problem in particle dynamics. The energy approach works most easily with forces and

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## This note was uploaded on 10/14/2011 for the course ENGINEER CHEM ENG 3 taught by Professor Ghosh during the Spring '11 term at McMaster University.

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lecture19 - Work and Kinetic Energy Work by a variable...

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