# A navy jet with a weight of 231 kN requires an airspeed of 85 m/s for liftoff. The engine develops a maximum force of 107 kN, but that is insufficient for reaching takeoff speed in the 90 m runway available on an aircraft carrier. What minimum force (assumed constant) is needed from the catapult that is used to help launch the jet? Assume that the catapult and the jet's engine each exert a constant force over the 90 m distance useed for takeoff.

I can't figure out the equation for this problem to get me started.

There is no single formula to memorize and look up to do this problem. You have to do it one step at a time, using formulas you should know.
The plane has to develop a speed of V = 85 m/s in X = 90 meters. That requires an acceleration a given by
V = sqrt (2 a X)
Solve for a.
a = V^2/(2X)
The total force needed to accelerate the plane is given by F = ma, where m = (231/kN/9.8 m/s^2) = 23570 kg.
Compute F.
There is already 107 kN of force provided by the engimes. The difference between F and that number must be provided by the catapult.

Please try to fill in the missing steps. If you need additional help, show your work.

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