Question 1
At the earth's surface the usual value for the acceleration due to gravity, g, is 9.8 m s-2. For an object falling downwards, what does this mean?
The right answer is the one marked above.
The object's velocity increases by 9.8 m s-1 every second. Acceleration is the change of velocity per second — which is why the unit m s-2 should be read as "metres per second, per second".
For an object starting to fall from rest, the velocity goes 0, 9.8, 19.6, 29.4 m s-1, and so on.
This is not a constant velocity — the velocity keeps growing. Nor does the object fall 9.8 m each second; because the velocity is increasing, the distance covered in each successive second increases too. The mass does not change at all.