m = 20 t = 20,000 kg.
V = 800 km / h = 222 m / s.
h = 3 km = 3000 m.
g = 9.8 m / s ^ 2.
The total mechanical energy E is the sum of the kinetic energy of motion Ek and the potential energy Ep of the aircraft.
The kinetic energy of motion Ek is determined by the formula: Ek = m * V ^ 2/2, where m is the mass of the aircraft, V is the speed of movement.
The potential energy of the aircraft Еп is determined by the formula: Еп = m * g * h, where g is the acceleration of gravity, h is the height of the aircraft above the earth’s surface.
E = m * V ^ 2/2 + m * g * h.
E = 20,000 kg * (222 m / s) ^ 2/2 + 20,000 kg * 9.8 m / s ^ 2 * 3000 m = 1080840000 J = 1 GJ.
Answer: the plane has total mechanical energy E = 1 GJ.
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