# Reactionary force to friction

1. Apr 8, 2008

### sarm2005

Ok so you push a box forward and the box exerts a force of friction backwards

Would the reactionary force to the friction on the box (the ground pushing the box backwards) be the force of the box pushing the ground forwards

2. Apr 8, 2008

### jae05

yea. that's given by N3L. but it's much more conveinent to think in terms of $$F_{fric}=\mu N$$. calculating the entire shift of the earth everything we wanna do a frictional problem's a bit of a stretch :D

3. Apr 8, 2008

### sarm2005

I wasn't actually trying to calculate it. Just making sure I understand newton's 3rd law.