- #1

MsMoser

- 3

- 1

^{2}, while the text handled it as "g" = 9.81 m/s

^{2}, and negatives are assigned directionally.

Overall, my approach (I felt) simplified calculations.

When we do sum of forces I handled it as actually adding forces on each axis and assigning + or - to the force as indicated by cartesian direction (since "g" is negative, this automatically makes F

_{g}a negative number. Life is good!

If on the y-axis a=zero then ΣF

_{y}= F

_{g}+ F

_{n}=0, therefore F

_{n}is positive. Life is still good!

When things begin to move on the x and we often default to the acceleration being in the positive direction, then F

_{k}, is a negative. OK, seems reasonable.

Then we get to μ!

μ

_{k}= F

_{k}/F

_{n}.

When using this to create an expression for F

_{n}, this almost always renders a negative normal force! This makes it difficult to just trust the signs and be careful with the algebra. Sigh.

I muddle through it with some fudging every year, but I want to do better than that. Help! Should I just go back and train myself to handle it the way the text does? Is there some brilliant 3rd road that I am missing?

Thanks in advance.