Question

8-An unidentified flying object (UFO) is observed to travel a total distance of 39000 m, starting and ending at rest, over a duration of 1.32 s. Assuming the UFO accelerated at a constant rate to the midpoint of its journey and then decelerated at a constant rate the rest of the way, what was the magnitude of its acceleration? Express your answer in g s , where 1 g = 9.81 m/s^2.

Answer 1

if a is acceleration in the first half journey in a time duration t₁ seconds,

then for the distance S₁ traveled by UFO, we have, S₁ = (1/2) a t₁² = 19500 ................(1)

After mid way, if UFO decelerates to travel same distance of 19500 m and comes to rest,

then magnitude of deceleration and magnitude of acceleration are same.

Also time duration of decelerated motion and time duration of accelerated motion are equal

hence t₁ = 1.32 / 2 = 0.66 s

From eqn.(1), we get, acceleration a = 39000/ (0.66)² = 89532 m/s²

acceleration a in terms of g = 89532/9.8 = 9136 g