A helicopter, starting from rest, accelerates straight up from the roof of a hospital. The lifting force does work in raising the helicopter

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 790-kg helicopter rises from rest to a speed of 7.0 m/s in a time of 3.0 s. During this time it climbs to a height of 7.2 m. What is the average power generated by the lifting force?

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Diễm Kiều 4 months 2021-09-05T04:41:30+00:00 1 Answers 49 views 0

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    2021-09-05T04:43:06+00:00

    Answer:

    25032.47 W

    Explanation:

    Power is the time rate of doing work, hence,

    P = Work done(non conservative) / time

    Work done (non conservative) is given as:

    W = total K. E. + total P. E.

    Total K. E. = 0.5mv²- 0.5mu²

    Where v (final velocity) = 7.0m/s, u (initial velocity) = 0m/s

    Total P. E. = mgh(f) – mgh(i)

    Where h(f) (final height) = 7.2m, h(i) (initial height) = 0 m

    => W = 0.5mv² – mgh(f)

    P = [0.5mv² – mgh(f)] / t

    P = [(0.5*790*7²) – (790*9.8*7.2)] / 3

    P = (19355 + 55742.4) / 3 = 75097.4/3

    P = 25032.47 W

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