Unformatted text preview: Kinetic Energy K = ½ mv 2 , K can never be negative Energy unit: 1J=1kg•m 2 •s2 Work  Kinetic Energy Theorem: ΔK= K – K =W (work) Work Work for constant force  1d: W = FΔx Work for constant force  3d: W=FΔr cos FΔr ⌠x  Work done by a variable force, 1d case: W= ⌡ x o F(x’)dx  ⌠r Most general 3d case:  W=⌡r o F(r’)*dr Work done against gravity: W g = mgh Work changing length of spring: W = ½ kx 2 + ½ kx 2 Power Definition of power as the rate at which work is done: P = dW/dt Average power over a time interval Δt: P = W/ Δt Unit of power (SI): 1 W = 1 J/s Unit of power (nonSI): 1 hp = 550 ft lb/s = 746 W Common energy unit: 1 kWh = 3.6•10 6 J = 3.6 MJ Power for constant force P = Fv cosα Fv Potential Energy Gravitational Potential Energy U g =  Wg (0 y ) = mgy Changing Gravitational Potential Energy: Δ Ug =  W g Gravity U g ( y ) = mgy + constant Spring force U s ( x ) = ½ kx 2 + constant F(x)=(dU(x))/dx U=mgh Pendulum: E=mgl(1cosθ)+ ½mv 2...
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This note was uploaded on 04/03/2008 for the course PHY 231 taught by Professor Smith during the Spring '08 term at Michigan State University.
 Spring '08
 smith
 Energy, Force, Kinetic Energy, Work

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