3 A De Havilland Otter aircraft with a mass of 2000 kg start

3. A De Havilland Otter aircraft with a mass of 2,000 kg starts from rest at sea level and takes off, then flies to a cruising speed of 240 km/h and altitude of 1 km. Assume g = 9.8 m/s² throughout the process.

a. What is the aircraft’s change in potential energy?

b. What is the aircraft’s change in kinetic energy?

Answers: About 20 and 4 MJ, respectively. PLEASE SHOW ALL WORK

Solution

a) change in Potential Energy

i) Initial pothential Energy

Potential Energy at ground level (mgh)₁=2000*9.81*0   (as height at ground level is zero)

                                                              = 0

Potential Energy at ground level (mgh)₂=2000*9.81*1000   (1km=1000m)

                                                              =19620000J

                                                              =1.96MJ (approxiamtely 2MJ by rounding it off)

Change in Potential Energy                   = (mgh)₂-(mgh)₁

                                                                                   =2-0

                                                              =2MJ

b) Change in Kinetic Energy

We Know Kinetic Energy K.E= 1/2mv²

where V is velocity

Intially K.E is Zero as the velocity of the flight at starting is Zero

therefore K.E₁=0

Final Kinetic Energy K.E₂=(1/2)*mv² =(1/2)*2000*66.666²           (240Km/hr=66.67 m/sec)

                                                         =4.44MJ (round off value to 4 MJ)

Change in K.E= final K.E-Initial K.E

                       =4-0=4MJ