(adsbygoogle = window.adsbygoogle || []).push({}); minus sign in "forces in space" problem.

1. The problem statement, all variables and given/known data

see picture for problem.

2. Relevant equations

please see a picture (one is of problem, the other contains the relevant formula).

3. The attempt at a solution

I was able to solve the whole thing, then looked at the solution, and saw that I missed a minus sign (which changed some, but not all of my solutions). I just don't understand why that minus sign (denoted by red arrow) is necessary (besides giving you the right answer). Generally, how do you think through it to know you need one there? Thanks for you help.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Minus sign in forces in space problem.

**Physics Forums | Science Articles, Homework Help, Discussion**