It seems like there's a bit of a mix-up in the question! Here's why and how to fix it:

* Units: Acceleration is measured in meters per second *squared* (m/s²), not "15 squared".

* Time: You need to specify the time the plane accelerates for (in seconds) to calculate the final speed.

Here's how to calculate the final speed:

1. Understanding the Concept: Acceleration tells us how much the speed changes every second. If the plane accelerates at 15 m/s², its speed increases by 15 meters per second every second.

2. The Formula: We use the following formula:

* Final Speed (v) = Initial Speed (u) + (Acceleration (a) × Time (t))

3. Applying it:

* Initial Speed (u) = 0 m/s

* Acceleration (a) = 15 m/s²

* Time (t) = 10 seconds (assuming this is what you meant)

Final Speed (v) = 0 + (15 × 10) = 150 m/s

Therefore, if the plane accelerates at 15 m/s² for 10 seconds, its final speed would be 150 m/s.