posted by joe .
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 runway.
If a plane of mass 2.10×105kg is to stop from a speed of 30.0m/s on a 120m long stretch of formcrete, what is the magnitude of the average force exerted on the plane by the formcrete?
F=ma=m v²/2s =2.1•10⁵•30²/2•120 = 787500 N