Question

The power of a motor is 60kW. At what speed can it raise a load of 50000

Answer 1

Well right off the bat, you've handed us a serious problem.  You left the unit off of the 50,000, so we don't know the single most important thing that we need to know about the load.

Is the load 50,000 kilograms ? 50,000 Newtons ? 50,000 pounds ?  Each of these will have a different answer.

Since you didn't specify the unit, I can make it anything I want, and I can pick the unit to make the problem easy to solve.  

So I'm going to say that the load weighs 50,000 Newtons, and now I shall proceed to solve the problem that I have invented.

If you're using a motor that's marked "60 kW", that number is the maximum safe power the motor can deliver without overheating and breaking down.  In order to raise our 50,000N load as fast as possible, we'll run the motor at its maximum rated power of 60 kW.  That means it'll do 60,000 Joules of work for us every second.

Power = 60,000 Joules/second

Power = 60,000 Newton-meters/second

60,000 Newton-meters/sec = (50,000 Newton) x S meters/sec.

Divide each side by 50,000 Newtons:

S = (60,000 Newton-m/sec) / (50,000 Newton)

S = (60,000/50,000) meter/sec

Speed = 1.2 meters/sec

Our 60 kW motor can raise the load at the speed of 1.2 m/s or any slower, but no faster than that.