Homework Help: physics

Posted by henry on Tuesday, November 8, 2011 at 8:59am.

If a man has an average useful power output of 31 W, what is the minimum time, in s, it would take him to lift fifty 12.3 kg boxes a height of 2.3 m.

i'm not sure how to go about it if anyone can help me
Thanks

physics - Henry, Wednesday, November 9, 2011 at 7:10pm
Wb = mg = 50*12.3kg * 9.8N/kg = 6027N. = Weight of 50 boxes.

Work = Fd = 6027 * 2.3 = 13,862 Joules.

31W. = 31Joules/s.

t = 13,862J. * (1/31)s/J. = 447.2s

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