Unless otherwise stated, all objects are located near the Earth\'s surface, wher

Question

Unless otherwise stated, all objects are located near the Earth's surface, where g = 9.80 m/s2 .
At the end of most landing runways in airports, an extension of the runway is constructed using a special substance called formcrete. Formcrete can support the weight of cars, but crumbles under the weight of airplanes to slow them down if they run off the end of a runwa

If a plane of mass 1.80×105 kg is to stop from a speed of 20.0 m/s on a 120 m long stretch of formcrete, what is the magnitude of the average force exerted on the plane by the formcrete?

Explanation / Answer

Solution:

Mass of the plane = m = 1.8 e5 kg

Initial speed = vi = 20 m/s

Final speed = vf = 0 (Plane Stops)

Length of the runway = 120 m

Acceleration of the plane = a = (vf2 - vi2 ) / 2d

                                              = (02 - 202) /(2*120)

                                              = -1.67 m/s/s

Acceleration is negative since the plane stops finally.

Average force = ma = (1.8 e5)(-1.67)

                                  = -3.0 x 105 N

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