(a) The work done by force in lb-ft is 300 lb-ft.
(b) The change in potential energy of the object is 200 lb-ft.
The work done by force in lb-ft is calculated as follows;
W = Fd
W = 30 x 10
W = 300 lb-ft
The change in potential energy of the object is calculated as follows;
ΔP.E = P.Ef - P.Ei
ΔP.E = 20 x 10 - 0 = 200 lb-ft
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