Question

A helicopter, starting from rest, accelerates straight up from the roof of a hospital. The lifting force does work in raising the helicopter. (a) What type(s) of energy is (are) changing? ls each type increasing or decreasing ? Why? (b) How is (are) the type(s) of energy that is (are) changing related to the work done by the lifting force? (c) If you want to determine the average power generated by the lifting force, what other variable besides the work must be known? An 810-kg helicopter rises from rest to a speed of 7.0 m/s in a time of 3.5 s. During this time it climbs to a height of 8.2 m. What is the average power generated by the lifting force?

Answer 1

Answer:

24.3KW

Explanation:

A)The kinetic energy is changing, the potential energy is changing and the chemical energy in form of fuel powering the engine also is changing

The kinetic energy is increasing as the body gain speed, the potential energy also increases as the body gain height against gravity and the chemical energy in form of fuel decreases as the body burn the fuel to create a lifting force

B) The workdone by the lifting force = the change in kinetic energy + the change in potential energy

C)The time taken in seconds to do the work is the variable needed

D) average power generated by the lifting force = (change in kinetic energy + change in potential energy) / time taken in seconds

Average power = 1/2 * m(mass) (Vf-Vi)^2 + mg(hf-hi) /t where vf is final speed and vi is initial speed at rest = 0, similarly, hf = final height and hi = initial height.

Average power = 1/2*810*7^2 + 810*9.81*8.2/3.5s

Average power = (19845+65158.02)/3.5 = 24286.577 approx 24.3kW