z_Ch7_lecture_notes_P195_Work_and_Energy

# z_Ch7_lecture_notes_P195_Work_and_Energy - Work and Energy...

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1 Work and Energy Recall from Ch4: Force: any agent of change . Energy, ~ E , is the capacity a body or system has to cause . Work is Energy transferred to (+) or removed from (-) a system or body by means of a force acting on it. Work and Energy are scalars.

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2 The Work done by the force F on the box is: Work = (the component of the force along the direction of motion) x (the distance thru which that component acts) W = F x ∆x (units??) W = Fcos θ ∆x = F ∆x ) x , F ( cos r r F Moving F x = F cos θ b x B θ
3 For a constant force F: W = F x ∆x but F = ma So W = ma ∆x use the 3 rd eq of motion… W = ½mv f 2 - ½mv o 2 The quantity ½mv 2 is called the KINETIC ENERGY. K = ½mv 2 F Moving F v 0 v f b x B

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4 KE is the energy a body or system has due to its motion. UNITS?? Note: KE 0 why? So, W = ½mv f 2 - ½mv o 2 becomes W = K f - K o or W net = ∆K Work-Energy Theorem Work-Energy Theorem : = The net work done by all external forces The change in Kinetic Energy
Or, more intuitively: K f = K o + W net Thus, when a force F does work on an object, that object will acquire a KE of ½ m v 2 . Let’s consider the Work done by:

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## z_Ch7_lecture_notes_P195_Work_and_Energy - Work and Energy...

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