Forces & Motion

What you’ll learn

• A force is a push or pull measured in newtons; the net force is the sum of all forces acting on an object.
• Newton's First Law: objects keep doing what they are doing (rest or steady motion) unless an unbalanced force acts; this is inertia.
• Newton's Second Law: net force equals mass times acceleration (F = ma); more force means more acceleration, more mass means less.
• Newton's Third Law: forces come in equal, opposite pairs that act on two different objects.
• Mass (kg) is how much matter you have and never changes; weight (N) is the force of gravity on that mass and depends on location.
• Momentum (p = mv) is conserved in a closed system when no outside net force acts.