How do you calculate the average acceleration of an object in m/s2

Atrain departs from its station at a constant acceleration of 5 m/s. what is the speed of the train at the end of 20s?

Agas initially at p1 = 1 bar and occupying a volume of 0.5 liter is compressed within a piston–cylinder assembly to a final pressure p2 = 4 bar. (a) if the relationship between pressure and volume during the compression is pv = constant, determine the volume, in liters, at a pressure of 3 bar. (b) repeat for a linear pressure–volume relationship between the same end states. reference

Which planet do you think would be easiest for humans to colonize some day?