How do I solve the following problem?(I don't understand how 1 & 2 are different)
Using Galileo's kinematical law (which I believe is D=16t^2) find:
1) The distance an object has fallen at 3.5 seconds.
2) The total distance the object has fallen in 3.5 seconds.
I don't think you've provided us with enough information to answer this question. What is the starting position of the object? Was it launched with some specific velocity at some specific angle?
That said, I'll try to give you my interpretation of the difference between (1) and (2).
In part (1), it is possible that the object went up before it went down. For example, if the object was launched off the top of a building at a positive angle, at 1 second maybe it's above the roof of the building, but at 3.5 seconds, it's below the roof of the build. This is asking how far below the starting point is the object.
In part (2), I think it may be asking the total distance travelled by the object. To find this, you must calculate the arc length of the parabola from the starting point to the point at 3.5 seconds.