Question

HELP! A helicopter winches up an injured person from a boat. The person plus the equipment that must be pulled up with the person has a mass of 109 kg. The efficiency of the motor (the actual work done divided by the electrical energy consumed expressed as a percentage) is 69%. If the height of the lift is 83 m and it is carried out at a uniform rate over 55 s, what is the power expended by the helicopter's winch motor? (Give your answer in Watts)

Answer 1

When a person is pulled upwards why the motor of the helicopter

Then the potential energy increased of the person is given as

`U = mgh`

here m = 109 kg

h = 83 m

so here potential energy of the person given as

`U = 109*9.8*83`

`U = 88660.6 J`

now power is defined as rate of energy

so it took 55 s to pull the mass so power is given as

`P = (U)/(t) = (88660.6)/(55) = 1612 W`

now we know that efficiency of motor is given as 69%

so we have

`0.69 = (1612)/(P)`

so we have power as

`P = (1612)/(0.69) = 2336.2 W`