What does the path of an object look like when it is in uniform motion?

Which of the following is true for displacement?

$A$ ball is gently dropped from a height of $20 \, m$. If its velocity increases uniformly at the rate of $10 \, m s^{-2}$,with what velocity will it strike the ground? After what time will it strike the ground?

$A$ train starting from a railway station and moving with uniform acceleration attains a speed $40 \, km \, h^{-1}$ in $10$ minutes. Find its acceleration (in $m / s^{2}$).

$A$ bus decreases its speed from $80 \, km \, h^{-1}$ to $60 \, km \, h^{-1}$ in $5 \, s$. Find the acceleration (in $m / s^2$) of the bus.

What is the nature of the distance-time graphs for uniform and non-uniform motion of an object?