Answer to Question #156098 in Physics for Arvin Shopon

Question #156098

A passenger aircraft with a mass of 78,000 kg flies at a cruising altitude of 11,300 m at a speed of 864 km/h. How big is it


a) kinetic energy

b) potential energy in relation to the ground

c) mechanical energy?


1
Expert's answer
2021-01-16T17:22:23-0500

a) We can find the kinetic energy from the formula:


KE=12mv2,KE=\dfrac{1}{2}mv^2,

KE=1278000 kg(864 kmh1000 m1 km3600 s1 h)2=2.25109 J.KE=\dfrac{1}{2}\cdot78000\ kg\cdot(864\ \dfrac{km}{h}\cdot\dfrac{1000\ m}{1\ km}\cdot\dfrac{3600\ s}{1\ h})^2=2.25\cdot10^9\ J.

b) We can find the potential energy in relation to the ground from the formula:


PE=mgh,PE=mgh,PE=78000 kg9.8 ms211300 m=8.64109 J.PE=78000\ kg\cdot9.8\ \dfrac{m}{s^2}\cdot11300\ m=8.64\cdot10^9\ J.

c) By the definition of the mechanical energy, we have:


E=PE+KE,E=PE+KE,E=8.64109 J+2.25109 J=1.091010 J.E=8.64\cdot10^9\ J+2.25\cdot10^9\ J=1.09\cdot10^{10}\ J.

Answer:

a) KE=2.25109 J.KE=2.25\cdot10^9\ J.

b) PE=8.64109 J.PE=8.64\cdot10^9\ J.

c) E=1.091010 J.E=1.09\cdot10^{10}\ J.


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