resultant forces

• a resultant force is a single force which replaces several other forces. it has the same effect acting on the object as the combination of the other forces it has replaced.
• the forces are represented in a free body diagram where the arrows are relative to the magnitude and direction of the force.
• when the resultant force is not zero, an object will change speed (accelerate or decelerate) or change direction (or both).
• when an object is stationary, there are still forces acting on it.
• when forces are balanced (in equilibrium), an object will either remain stationary or if it's moving, it will continue to move at a constant speed.