1. Forces, Net Force & Balanced Forces

A force is a push or pull. Forces can start motion, stop motion, speed something up, slow it down, or change direction. The important idea is net force: the overall force after all pushes and pulls are combined.

If forces are balanced, net force is zero and motion does not change. If forces are unbalanced, motion changes.

Deep explanation. A force is a vector, meaning it has both size and direction. Net force is the overall force after all pushes and pulls are combined. If two equal forces pull in opposite directions, they cancel. If one force is larger, the object accelerates in the direction of the larger force.

Balanced forces do not always mean an object is sitting still. They mean the object's motion is not changing. A book at rest on a table has balanced forces. A hockey puck sliding at constant velocity on nearly frictionless ice also has balanced forces because its speed and direction stay constant.

GED® routine. Draw arrows mentally or on scratch paper. Add forces in the same direction. Subtract forces in opposite directions. If the net force is zero, motion stays the same. If the net force is not zero, velocity changes.

⚠️ Common misconception: an object moving at constant speed needs a net force to keep moving. With no net force, it keeps moving at constant velocity.

💡 Tip: unbalanced force changes motion.