Physics Problem.... completely lost....?

Question

A Boeing 777 can accelerate from 0 to 70 m/s in about 28 seconds. Determine the average power developed by the jet engines assuming that the mass of the plane is 136,000 kg. Divide your answer by 750 to see the average horsepower developed by the engines.

Answer 1

The formula for kinetic energy is:
T = 1/2*m*v^2

You know the kinetic energy of the plane at rest; it's zero. The kinetic energy of the plane at 70 m/s is:
T = 1/2*(136000 kg)*(70 m/s)^2
T = 333,200,000 joules

Now, average power is simply the amount of energy (T) generated, divide by the amount of time (t) to generate it:
P = T/t
P = (333,200,000 joules) / (28 seconds)
P = 11,900,000 watts

To go from watts to horsepower, divide by 745.7 (but 750 is a close enough approximation):
11,900,000 / 750 = about 16,000 horsepower

Answer 2

Energy E = 1/2 * m * v^2

E = 0.5 * 136,000 kg * (70 m/s)^2 = 333,200,000 J
Power P = E / t = 333,200,000 J / 28s = 11,900,000 W

11,900,000 / 750 = 15,867

Answer 3

Power = Force x delta v
Force = mass x acceleration
Acceleration = delta v / delta t

Substituting,

Power = mass x (delta v)^2 / delta t

Power = 136,000 x (70 - 0)^2 / 28

Power = 23.8 MW

Power = 23.8 x 10^6 W * 1 HP / 747 W (747 W per HP, approx.)

Power ~= 31,861 HP

Answer 4

Franki ah would lurv to help but ah am so darn confounded with this question. Ah nevuh was an expert with the Van de Graaff generator.