88.1 Work done by variable force 3. The work done by a constant force W=F.Scos6=F·S 4. The work done by variable force differential work b dw s F dr F.dr. cos 0 Fcos ads F 88.1 Work done by variable force Define the differential work done by any force is dW= fdr The work done by a particular force eis w=dw=Fdr In Cartesian coordinate system W=(Fi+E,j+F) dr d b dxi+dvj+dzk) (F dr+ f dy+F,dz) F2 W F S F S v v = ⋅ ⋅ cosθ = ⋅ θ F v s v F v 3. The work done by a constant force F s F r W F r cos d d cos d d θ θ = = ⋅ ⋅ = ⋅ v v v differential work a b o F v r v d ds r v r′ v θ F r 4. The work done by variable force §8.1 Work done by variable force §8.1 Work done by variable force Define the differential work done by any force is W F r r r d = ⋅d The work done by a particular force is F r ∫ ∫ = = ⋅ f i W F r r r W d d In Cartesian coordinate system: ( d d d ) )ˆ d ˆ d ˆ (d ) ˆ ˆ ˆ W ( F x F y F z xi yj zk F i F j F k y z r r x y z r r x f i f i = + + + + = + + ⋅ ∫ ∫ r r r r a b o F v r v d ds r v r′ v θ F r