Question

I think the solutions to the Concept Questions for Module 3 (http://ocw.mit.edu/courses/physics/8-01sc-physics-i-classical-mechanics-fall-2010/cartesian-coordinates-and-vectors) have an error.

The answer to Question 4 should be "Answer 3" - that's what's described.

Answer 1

No, the answer to the question is (2). A unit vector has length 1, so if
\[ |\vec{A}|>1\]
then to make it a unit vector you must divide by its magnitude,
\[ \frac{\vec{A}}{|\vec{A}|} \]

Answer 2

I just looked at the solution though, and you are correct, it is a typo, but I think you may have made a typo in your question here, because you seem to be advocating the same answer as is written there...

Answer 3

Thanks - my mistake! I meant to say it should be "Answer 2."