(Solved): 29) A crane lifts a 425kg steel beam vertically a distance of 117m. How much work does the cra ...

29) A crane lifts a $$425\mathrm{kg}$$ steel beam vertically a distance of $$117\mathrm{m}$$. How much work does the crane do on the beam if the beam accelerates upward at $$1.8\mathrm{m}/\mathrm{s}2$$ ? Neglect frictional forces. A. $$5.8\times 10^5\mathrm{J}$$ B) $$3.4\times 10^5\mathrm{J}$$ C) $$4.0\times 105\mathrm{J}$$ D) $$4.9\times 105\mathrm{J}$$ 30) In the figure, a constant external force $$P=160\mathrm{N}$$ is applied to a $$20.0?\mathrm{kg}$$ box, which is on a rough horizontal surface. While the force pushes the box a distance of $$8.00\mathrm{m}$$, the speed changes from $$0.500\mathrm{m}/\mathrm{s}$$ to $$2.60\mathrm{m}/\mathrm{s}$$. The work done by friction during this process is closest to (A) $$?1040\mathrm{J}$$ B) $$+1110\mathrm{J}$$ C) $$+1170\mathrm{J}$$ D) $$+1040\mathrm{J}$$ E) $$?1170\mathrm{J}$$