an airplane has a takeoff speed of 80 meters per second which it reaches 35 seconds after starting from rest. What is the minimum length of the runway?

Answer 1

Start by calculating the acceleration of the plane as it moves from rest to take-off. It gets up to 80 m/s in 35 seconds, so its acceleration is 80/35 m/s^2.

Now you can just plug in the formula for distance travelled under acceleration = ut + 0.5at^2.

Initial velocity u is zero. We've worked out the acceleration, and we know that t=35sec. The rest is easy.