(a) How long would it take a 1.00 10 5 kg airplane with engines that produce a m

Question

(a) How long would it take a 1.00 105 kg airplane with engines that produce a maximum of 100 MW of power to reach a speed of 300 m/s and an altitude of 12.0 km if air resistance were negligible?
Answer in terms of s

(b) If it actually takes 925 s, what is the power applied, in megawatts?
Answer in terms of MW

(c) Given this power, what is the average force of air resistance if the airplane takes 1200 s? (Hint: You must find the distance the plane travels in 1200 s assuming constant acceleration.)
Answer in terms of kN

Explanation / Answer

here,

a)

KE = 0.5 * mv^2 = 0.5 * 1 * 10^5kg * (300m/s)^2 = 4.5 GJ

PE = mgh = 1* 10^5kg * 9.8m/s^2 * 1.2* 10^4m = 11.8 GJ

total work done = 16.3 MJ

time = work / power = 16.3GJ / 100MW = 163 s

time taken is 163 s

b)

power = work / time

P = 16.3GJ / 925s

P = 17.6 MW

the power applied is 17.6 MW

c)

total work = 17.6MW * 1200s = 21.1 GJ
minus the KE and PE leaves friction work = 4.83 GJ

a = v / t = 300m/s / 1200s = 0.25 m/s^2

s = 0.5 * at^2 = 0.5 * * 0.25m/s^2 * (1200s)^2 = 1.80 * 10^5 m

friction force F = work / distance = 4.83GJ / 1.80* 10^5m

frictional force = 26.8 kN

the frictional force is 26.8 KN

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