1. The problem statement, all variables and given/known data An Airbus 380 needs to reach the velocity of 280 kmh^-1 before it takes off. The maximum acceleration the plain reaches in the runway is 0.95 ms^-2. Verify THAT the plane can use an airport with this runways. Runway 1: 3805 meters (SSW-NNE) Runway 2: 2400 meters (S-N) 2. Relevant equations $$x=x_0+v_0 t + 1/2 a t^2 $$ $$ v= v_0 + at $$ 3. The attempt at a solution At first I thought this was a pretty easy problem. Using equations of motion: $$x=1/2 a t^2 $$ $$ v= at $$ For the first runway, solving $$3805=1/2 \times 0.95 \times t^2$$ $$t=89.5 s$$ $$v= 0.95 \times 89.5 $$ $$v=85.05 ms^-1$$ Which confirms it can use this runway (since the velocity is bigger than the necessary velocity). However for the second runway, I get $$2400=1/2 \times 0.95 \times t^2$$ $$t=71.1 s$$ $$v= 0.95 \times 71.1 $$ $$v=67.545 ms^-1$$ Which is inferior to the necessary velocity. But that contradicts the problem statement that it can indeed use the airport. I might be making an incorrect assumption. I suspect it might be related to the acceleration. In fact they say that's the maximum acceleration not the acceleration. So the might be a time dependence on the acceleration? But how do I determine it? Thanks!