Some Food for Thought....

Why do I (and Moore) make such a big deal about "please explain ..."

Writing is a fundamental mode of intellectual expression
and producing students with superior scientific writing skills
is a goal of many physics programs. The need for development
of good writing skills in all students has resulted in the
writing-across-the-curriculum initiative that recognizes the
importance of developing writing skills in all classes and the
usefulness of writing as a learning tool 1–3. Improvement
of the technical writing skills of physics students is often a
key goal of physics departments 2,4,5 and other science
departments 6,7. Writing is also frequently proposed as an
important method for improving student thinking skills or
understanding of a topic.

from Effect of written presentation on performance in introductory physics
John Stewart* and Shawn Ballard, Physics Education Research, Oct 2010

and from their conclusion...

This study sought to answer two questions:
1 to what
extent is the variance in student performance explained by
the quantitative features of student writing and
2 what features
of student writing are most important for performance?
The total amount of writing in nine categories explained
more variance in performance than any other single reported
measure.