Question

calculate the power of pump which can lift 500kg water at a height id 5m in 10 sec.

Answer 1

At what rate do you want to lift these 100 kg? Slower the rate, lesser would be the wattage rating.

Let's do a quick calculation here:

power = work/time

work = force x distance

So power = force x distance/time or equivalently,

power = force x speed of lifting (rate)

Force needed to hold 100 kg against gravity = 100*9.8, rounding it up to 1000N.

Let's say the machine lifts it up at a rate of 1 meter per second.

So power needed would be 1000 x 1 = 1kW.

But this is the power needed without frictional and other losses. Fairly assuming that the motor and pulley assembly is 80% efficient, actual power the motor pumps in from the source would be 1000/0.8 = 1.25kW.

This verifies the aforementioned fact that higher the rate with which the weight needs to be lifted, more would be the wattage rating.