1. A brief review of Forces Balanced and Unbalanced Contact and Action-at-a-Distance

2. Balanced vs Unbalanced Balanced Unbalanced If there is acceleration, then there is an unbalanced force. If acceleration is zero, then the forces are balanced.

3. Are these balanced or unbalanced forces? A Racecar at the start of a race.A car parked on the side of a hill. A minivan using cruise control, on a flat highway.

4. Remember: Acceleration is any change in velocity! Slowing down, Speeding up, or changing direction. Acceleration equals zero if an object is not moving, or if it is moving at a constant velocity.

5. Contact and Action-at-a-Distance Contact Forces- Those that need to physically touch an object. Action-at-a-Distance Forces- Those that do not need to touch an object.

6. Contact Forces Friction Tension Air Resistance Applied Spring Normal Action-at-a-Distance Forces Magnetic Electrical Gravitational