Question

7)A machine of efficiency 85% is used to lift a 1200 kg load to a height of 3
m in 120 seconds. Find:
i) the power of the machine.
ii)the energy consumed by the machine.

Answer 1

Answer:

From work energy theorem, 

Work done = change in potential energy

So, W=mgh

So, 0.75×12=1×10×h

So, h=0.9m

Now, from conservation of energy,

KE=PE

So, 21mv2=mgh

So, v=2gh=2×10×0.9=32m/s