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lecture19 - Work and Energy Newtons approach F = ma r r...

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1 Physics 1D03 - Lecture 19 Work and Energy a m F r r = Energy approach : Net work = increase in kinetic energy - acceleration at any instant is caused by forces - equivalent to Newton’s dynamics - scalars, not vectors - compares energies “before and after” Newton’s approach: Work ”: Serway 7.1—7.4 Practice: Chapter 7, Problems 1, 5, 7, 11, 13 Physics 1D03 - Lecture 19 “system” external environment heat flow mechanical work etc. Energy is conserved. Energy must flow into (or out of) a system from the outside universe by various processes. Mechanical work is one way of transferring energy.

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2 Physics 1D03 - Lecture 19 Work θ θ Work by a constant force F during a displacement s : s r II F F r F r Units : N • m = joule (J) Work = (component of F parallel to motion) x (distance) We can also write this as This is the “scalar product”, or “dot product”. Work is a scalar . Work = F s Physics 1D03 - Lecture 19 Example (massless pulleys, no friction) s = 2 m How much work is done on the rope by F p ?
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lecture19 - Work and Energy Newtons approach F = ma r r...

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