Gravity (weight) pulls down

Normal force/support force pushes up from a surface

Applied force (push/pull) from a person or another object

Tension from a rope/string (if present)

Friction is an external force

Air resistance/drag (if moving through air)

Balanced forces → net force = 0

Unbalanced forces → net force ≠ 0

Object remains at rest or keeps moving at constant speed in a straight line

Objects at rest stay at rest (unless a net external force acts)

Motion changes (speed changes or direction changes)

The object accelerates

“An object at rest stays at rest, and an object in motion stays in motion at constant velocity, unless acted on by a net external force.”

If it slowed down: identify the net external force (often friction or air resistance)

If it started moving: identify the applied force causing a net force

If it kept moving steadily: explain that forces are balanced (net force = 0)