A hot air balloon with a total mass of200kg is equipped with a large natural gas

Question

A hot air balloon with a total mass of200kg is equipped with a large natural gas tank that has an initial internal energy of 500kJ before take-off. The hot air balloon uses the natural gas to heat up the air inside the balloon providing lift and powers a small propeller engine which can move the balloon left/right/forward/backward. At one point during the flight, the internal energy of the tank is 200k, the balloon is at an altitude of 100m and is moving at a speed of 10m/s. Determine the change in potential energy of the system [kJ] Determine the change in kinetic energy of the system [kJ] Determine the amount of energy which has crossed system boundaries [kJ]

Explanation / Answer

Given

total mass of system = m =200 kg

Initial Internal energy = Ui = 500 KJ

Final internal Energy = Uf = 200 kJ

height = h = 100 m

speed = v = 10m/s

a) change is potential energy = mgh - 0 = 200 * 9.8 * 100 = 196 kJ

b) change in kinetic energy = mv2/ 2 - 0 = 200 * 102/2 = 10 kJ

c) Energy crossed the boundry = loss in energy = 500 -10- 196 - 200 = 94 kJ

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