A fighter jet is launched from an aircraft carrier with the aid of its own engin

Question

A fighter jet is launched from an aircraft carrier with the aid of its own engines and a steam-powered catapult. The thrust of its engines is 2.12 x 105 N. In being launched from rest it moves through a distance of 87.8 m and has a kinetic energy of 6.50 x 107 J at lift-off. What is the work done on the jet by the catapult?

A 17-kg sled is being pulled along the horizontal snow-covered ground by a horizontal force of 33 N. Starting from rest, the sled attains a speed of 2.5 m/s in 9.1 m. Find the coefficient of kinetic friction between the runners of the sled and the snow.

Explanation / Answer

kinetic energy at lift of is combination of energy produced by both catapult and jet engine.
jet engine contributes

K=F*d=(2.12 10^5)*87.8 =18613600 J
or
K=1.861*10^7J
since the total kinetic energy is E=6.50 10^7 J
work done by catapult is the difference:

W=E-K= 4.64 *10^7 J

Net force = mass * acceleration
The net force on the sled is equal to the horizontal force minus the friction force.

Net force = 33 – Ff = 17 * a
To determine the acceleration, use the following equation.

vf^2 = vi^2 + 2 * a * d, vi = 0
2.5^2 = 2 * a * 9.1
a = 6.25÷ 18.2
This is approximately 0.3434 m/s^2.

33 – Ff = 17 * 6.25 ÷ 18.2
Ff = 33 – 17 * 6.25÷ 18.2 = 27.16 N

Ff = * 17 * 9.81 = *166.77
* 166.77 = 27.16
= 27.16 ÷ 166.77 = 0.1628
This is approximately 0.16.

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