Final answer:
The average acceleration of the flying saucer, which moved from 20 m/s [E] to 50 m/s [W] in 3.8 seconds, is approximately -10 m/s² [W]. The answer takes into account the opposite directions of initial and final velocities and presents the acceleration as a vector quantity, resulting in negative acceleration towards the west.
Step-by-step explanation:
To find the average acceleration of a flying saucer, you can use the formula for acceleration, which is the change in velocity divided by the time it takes for the change. In this case, the flying saucer changes its speed from 20 m/s [E] to 50 m/s [W]. Since these velocities are in opposite directions, we consider the change to be 70 m/s. Remember to include the direction, as acceleration is a vector quantity.
We calculate the average acceleration as follows:
Final Velocity (Vf) = 50 m/s [W]
Initial Velocity (Vi) = 20 m/s [E] (which is equivalent to -20 m/s [W] when considering the opposite direction)
Time (t) = 3.8 s
Acceleration (a) = (Vf - Vi) / t
The change in velocity (Vf - Vi) is 50 m/s [W] - (-20 m/s [W]) = 70 m/s [W].
So acceleration (a) = 70 m/s [W] / 3.8 s = 18.42 m/s² [W].
However, we consider negative acceleration since the flying saucer is decelerating in the [E] direction when accelerating towards the [W] direction. Therefore, the correct option, with the available choices being closest to our computed value, is (d) -10 m/s² [W].