What do you understand by the term acceleration? When is it positive and when is it negative?

$A$ body is thrown vertically upward with velocity $u$,the greatest height $h$ to which it will rise is,

Give one example for each of the type of motion when
$(i)$ acceleration is in the direction of motion.
$(ii)$ acceleration is against the direction of motion.
$(iii)$ acceleration is uniform.

The following graph describes the motion of a girl going to meet her friend who stays $50 \ m$ from her house.
$(i)$ How much time does she take to reach her friend's house?
$(ii)$ What is the distance travelled by the girl during the time-interval $0$ to $12$ minutes?
$(iii)$ During which time-interval is she moving towards her house?
$(iv)$ For how many minutes was she at rest during the entire journey?
$(v)$ Calculate the speed by which she returned home.

State whether the following statement is true or false:
$A$ motion is said to be uniform if $x \propto t^{2}$.

Prove that if a body is thrown vertically upward,the time of ascent is equal to the time of descent.