FORCES

Force  any push or pull  Example: opening a door  Pushing something across the floor

Balanced Forces Do not cause a change in motion. They are equal in size and opposite in direction. The forces cancel each other out Example: When arm wrestling neither arms are moving Pushing/Leaning against a person and neither moving

Unbalanced Forces  Always cause a change in motion. They are not equal and opposite.  Example: When arm wrestling, one person is stronger and their hand goes down (one person wins)  Pushing against a person and one person moves/falls

Friction  The force that one surface exerts on another when the two rub against each other  Example: When you roll a ball across the floor, it loses energy as it rolls due to friction

Inertia  An object at rest stays at rest, and an object in motion will stay in motion unless acted on by a force  Example: the ball would continue rolling across the floor if there was no friction (until it hit something that makes it stop)