PHYS171_f11_lecture_24

# PHYS171_f11_lecture_24 - pull with a force of 2 Newtons...

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PHYS171 Principles of Physics I Chapter 7 Definition of “Work” Work is when Force is Productive • When force is in the same direction as velocity, speed increases • When force is in the opposite direction as velocity, speed decreases • When force is perpendicular to velocity speed remains the same We need a quantity that reflects the extent to which force changes the quantity of motion of a free body. v F v F v F

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Chapter 7 Definition of “work” for a constant force When a particle moves a distance s under constant force F the work is the distance multiplied by the component of the force which is parallel to s s F Fs s F W r r = = = θ cos parallel s cos parallel F F = F r Chapter 7 Example I pull a block across the floor by pulling a string. The string makes a 30 degree angle with the horizontal and I
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Unformatted text preview: pull with a force of 2 Newtons, moving the block a total of 3 meters. s F Fs s F W r r ⋅ = = = cos parallel s cos parallel F F = F r Chapter 7 Definition of “work” for varying force When a particle moves a distance ds under constant force the work is the distance multiplied by the component of the force which is parallel to ds ∫ ⋅ = ⋅ = = s d F W s d F Fds dW r r r r θ cos ds F r cos parallel F F = Chapter 7 Definition of “work” varying force ∫ ⋅ = ⋅ = = s d F W s d F Fds dW r r r r cos F cos s When a particle moves a distance ds under constant force the work is the distance multiplied by the component of the force which is parallel to ds...
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## This note was uploaded on 12/29/2011 for the course PHYSICS 171 taught by Professor La porta during the Fall '11 term at Maryland.

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PHYS171_f11_lecture_24 - pull with a force of 2 Newtons...

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