Physics

Problem

An electric hoist draws

40\,\text{kW}

of electrical power and operates at

80\%

efficiency. It lifts a

500\,\text{kg}

load vertically from rest. Half of the useful mechanical power goes into increasing the load’s kinetic energy, while the other half goes into raising it against gravity. What is the speed of the load after

8\,\text{s}

? a)

20\,\text{m\,s}^{-1}

18\,\text{m\,s}^{-1}

25\,\text{m\,s}^{-1}

22.6\,\text{m\,s}^{-1}

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