Whats a good way to say "The main idea of this text is-"

The central point of the text is

Explanation:

You could also throw in the word introduction or thesis.

The plot

Explanation:

The purpose of this to to tell about it

the boy's acceleration toward the girl is 2.08 m/s^2.

explanation:

according the newton's third law, the force causing the girl accelerate towards the boy will be me with equal counter-force causing the boy to accelerate towards the girl. these forces will be of equal magnitude and allows us to determine the boy's acceleration:

the boy's acceleration toward the girl is 2.08 m/s^2.

reflexive.the third one.