Problem 21.

An aircraft has a lift-off of 120km/h.

(a) What minimum constant acceleration does the aircraft require if it is to be airborne after a takeoff run of 240m?

(b) How long does it take the aircraft to become airborne?

Solution:

(a) This is the motion with constant acceleration. We know that the initial velocity is 0. And we know that after run of 240 m the velocity of aircraft becomes 120 km/h = 120 *1000/3600 m/s = 33.3 m/s.

Then we need to use the following equation:

From this equation we can find acceleration:

(b) Now we know acceleration and we know the final velocity so we can find the traveled time: