An airplane is sitting on a runway waiting to take off. the airplane begins to move down the runway and it takes 10 s for the airplane to leave the ground. the speed of the airplane at takeoff is 40 m/s. what is the acceleration of the airplane while it is moving down the runway?

Acceleration = (change in speed) / (time for the change)

-- You said that the airplane has to speed up from zero ("sitting") to 40 m/s, so the change in speed is 40 m/s.

-- You said that it has to roll for 10 seconds to build up enough speed to take off, so the time for the change is 10 s .

Acceleration = (40 m/s) / (10 s)

Acceleration = (40/10) (m/s)/s

Acceleration = 4 m/s²

That seems like no problem.  It's only like about 41% of 1 G .  That would not even spill the drinks in First Class, or wake up the passengers who are already asleep (like me).

the speed of the cart after 3 seconds of low fan speed is ⇒ 54.0 cm/s.

the speed of the cart after 5 seconds of medium fan speed is ⇒ 120.0 cm/s.

the speed of the cart after 2 seconds of high fan speed is ⇒ 64.0 cm/s. 

just did the lab.