Double quotation marks are used: 1) whenever there is direct quotation
2) for internal dialogues

here's your

hope you

it could change in many ways and by that i mean income can go lower or higher depending on how hard you work. i hope this .

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.