Q:

Directional collision detection

If I want to move an object 40 pixels every second and I have the following scenario, how can I efficiently detect that there was a collision? 
Assume both objects are 10 by 10 squares
Starting point of moving object at 2 seconds:
40, 100
Ending point of moving object at 3 seconds:
80, 100
Stagnant object at 60, 100
If I am only moving the moving object once (from 40 to 80 without any movements in between) how would I tell there was an object between them?
This is obviously a simplified version of what I am doing but I wanted it to be easy to understand.
The only thing I can think of is check if each object has a side with an x value less than 80 and another side with an x value greater than 40 and the same idea with y values...
I'll be using javascript and html5 canvas if that makes any difference.

A:

You could try to determine if there was a collision with the bounding rectangle defined by the start and end positions of the moved object:
+-----------+--+
|     +==+  |  |
+-----:  :--+--+
      +==+

