My physics text says that force is "an interaction between two bodies or a body and its environment."  

When an object undergoes acceleration we explain it with a force.  But we don't measure force, we measure the change in acceleration. Is force just a helpful construct to be a placeholder in the equation F = ma?  

Is force defined as the quantity mass times acceleration, or is it really "an interaction"?   


Question: How to find bible verses?
Answer: I learned this technique on Protestant Bibles but you could easily adapt it for any Bible. It works best if you have everyone use their own Bible so that they can see how the technique applies to the Bible they use most.


Psalms is usually at the center of most Bibles. If you're looking for Psalms you try to open to the middle of the book.
The New Testament tends to start around the last quarter of the Bible.
So let's say you're looking for John 3:16.

It's in the New Testament so it's in the last quarter of the Bible.
It's a Gospel so it's at the front of that last quarter.
Flip to about the last quarter of the book. If you land on John great.
If you landed somewhere else is it before or after John?



This also goes hand in hand with memorizing the order of the books which the best I can do is a song that I think I might still have somewhere on VHS but you can just hit up YouTube and find something your kids will like.

Even more helpful is understanding the sections of the Bible.


Law
History
Poetry &amp; Wisdom
Major Prophets
Minor Prophets
Gospels
Pauline Epistles
General Epistles
Prophecy


So from the example above, if the open the Bible to somewhere other than John it goes:


What book are you on?
Is it before or after John?


Is it Old Testament or New? If it's old you move back. New could be either way.
What section is it in? If it's a Gospel, which one? (in this case any one means move back slowly)
If it's not at least one of the minor prophets then you're probably way too far ahead.
Likewise if you landed in Revelation then you're too far back. (This actually happens because of maps and other stuff they cram into Bibles these days.)



It plays out like a game of 20 questions. Every time you move you repeat the steps. I don't remember it taking long for us to pick this up but, the more time they spend using an actual Bible with no search aids, the faster they'll get it.