Question

a plane travelling north has a landing speed of 75.6m/s. after touch down it has 787m long runway to reduce its speed to 15.9m/s. calculate average acceleration of the plane during landing taking the direction of the plane travels as positive

Answer 1

if v is + and it slows down a is - , (deacceleration)
change in velocity = - 75.6

time to stop = distance /mean velocity = 787 / mean velocity
because velocity vs time is linear mean velocity = 75.6/2 = 37.8
so t = 787 /37.8 = 20.8 m/s

a = change in velocity / time = -75.6 / 20.8 m/s^2

Answer 2

so my answer is 13.21?

Answer 3

-75.6 divided by 20.8 is not 13.21