Help i dont get it?

Airplane A, starting from rest with constant acceleration, requires a runway 400 m long to become airborne. Airplane B requires a takeoff speed twice as great as that of airplane A, but has the same acceleration, and both planes start from rest. a) How long must the runway be for airplane B?


You are right about the 2t time, but for the second half of the 2t it will be going faster so it takes more than twice the distance. The position is given as 1/2at^2 so since the acceleration is constant it will 2t^2 will take 4 times the distance or 1600m


Sounds like its double the distance since it requires twice the speed with the same constant acceleration. so if you figure an 800m long runway, you'll go airborne..