This document defines key concepts about forces including: - A force is a push or pull exerted by one object on another. Forces have both direction and magnitude. - Forces can combine in the same or opposite directions. Forces adding in the same direction give the net force, while opposing forces subtract. - Balanced forces result in no motion, while unbalanced forces cause changes in motion. - There are contact forces like friction and gravity, as well as non-contact forces like magnetism and electricity. Friction opposes motion between surfaces.

1. The Physical World: Forces Ms. Novak 2008-2009

10. Equal Sized Forces Force 1 Force 2 15 N 15 N Force 1 – Force 2 = Net Force 15 N – 15 N = O N