Movement 43831

The crane motor has a constant power of 9 kW. With constant movement, how long does it take to lift a body weighing 12 tons to a height of 9 m?

Correct answer:

t =  120 s

Step-by-step explanation:

$$\begin{gathered} P=9\text{kW}\to \text{W}=9\cdot 1000\text{W}=9000\text{W} \\ m=12\text{t}\to \text{kg}=12\cdot 1000\text{kg}=12000\text{kg} \\ h=9\text{m} \\ g=10{\text{m/s}}^2 \\ F=m\cdot g=12000\cdot 10=120000\text{N} \\ W=F\cdot h=120000\cdot 9=1080000\text{J} \\ t=W/P=1080000/9000=120\text{s} \end{gathered}$$

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