A helicopter, starting from rest, accelerates straight up from the roof of a hos

Question

A helicopter, starting from rest, accelerates straight up from the roof of a hospital. The lifting force does work in raising the helicopter. An 880-kg helicopter rises from rest to a speed of 8.1 m/s in a time of 3.6 s. During this time it climbs to a height of 9.7 m. What is the average power generated by the lifting force?

I looked at the solution on cramster (ch 6, problem 64) and still can't get the right answer. By following this comment posted by an expert, I got F = 1980. Since W = F x distance I got W = (1980)x9.7 = 19206

P = W/ t
P = 19206 / 3.6 = 5335 Watts

But this is wrong..

Explanation / Answer

Given that mass = 880 kg speed v= 8.10 m/s height h = 9.70 m --------------------------------------------------------------------- The total energy is E = mgh + (1/2)mv^2 = (880.0 kg)(9.8 m/s2)(9.70 m) + (0.5)(880.0 kg)(8.10 m/s)^2 = 83652.8 J+ 28868.4 J = 1.125212x 10^+5 J the average power generated by the lifting force is P = E/t =(1.125212x 10^+5 J)/(3.60 s) = 3.1255 x10^+4 W

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