12.4 kw is used to raise a mass of 750 kg and is moved a distance of 3.5 m. how long did it take to lift the mass?

Question

roadjester · Answer

@LastDayWork 
I'm looking at this problem and it feels like I would need to know the acceleration.
$$P={W\over t}={F\Delta x\over t}={ma\Delta x\over t}$$
time is what i'm looking for, power is given, so is mass and displacement. Unless acceleration is simply g?

lastdaywork · Answer

@talita
Does "1.4 kw" implies kilo weight or kilo Watt ??

anonymous · Answer

You almost have it there. DeltaX = 3.5m. And F=mg. The assumptions are that:
1. Just enough force is applied so as to lift the mass;
2. The force applied is uniform over the time required to raise the mass.
So you put Acceleration=g=9.8m/s^2 and you are done!

anonymous · Answer

Clarification for Assumption 1: That means the mass does not gain any velocity as a result of the lifting, but just gains height.

anonymous · Answer

Calculate weight in Newton W=mg, then Workdone is Fxd, here F is your weight from first equation. Finally, use power, workdone and time relation to get time.