Force is a push or pull that can change an object's speed, direction, or shape. Newton's three laws of motion describe how forces affect objects.

Newton's First Law (Inertia): An object at rest stays at rest, and an object in motion stays in motion at constant velocity, unless a net external force acts on it. A ball on a table won't move unless pushed.

Newton's Second Law: Force = mass × acceleration (F = ma). A greater force produces greater acceleration. A more massive object needs more force to accelerate at the same rate.

Newton's Third Law: Every action has an equal and opposite reaction. When you push against a wall, the wall pushes back on you with equal force.

Friction is a force that opposes motion between surfaces in contact. Gravity is the force that pulls objects toward each other — on Earth, it accelerates objects downward at 9.8 m/s².