"Sir Isaac Newton's three laws of motion describe the motion of massive bodies and how they interact. While Newton's laws may seem obvious to us today, more than three centuries ago they were considered revolutionary. Extramarks gives you the best of explanations for Physics and Laws of Motion for you to help yourself excel the basics of Physics. Extramarks helps you understand the Laws of Motion through simple introductions, illustrations and examples. Have a sneak peek at the given introduction to Laws of Motion and the First Law of Motion states, ""A body at rest will remain at rest, and a body in motion will remain in motion unless it is acted upon by an external force."" This simply means that things cannot start, stop, or change direction all by themselves. It takes some force acting on them from the outside to cause such a change. This property of massive bodies to resist changes in their state of motion is sometimes called inertia while the Second Law of Motion describes what happens to a massive body when it is acted upon by an external force. It states, ""The force acting on an object is equal to the mass of that object times its acceleration."" This is written in mathematical form as F = ma, where F is a force, m is mass, and a is acceleration. The bold letters indicate that force and acceleration are vector quantities, which means they have both magnitude and direction. The force can be a single force, or it can be the vector sum of more than one force, which is the net force after all the forces are combined and the Third Law of Motion states, ""For every action, there is an equal and opposite reaction."" This law describes what happens to a body when it exerts a force on another body. Forces always occur in pairs, so when one body pushes against another, the second body pushes back just as hard. For instance, when you push a cart, the cart pushes back against you; when you pull on a rope, the rope pulls back against you; when gravity pulls you down against the ground, the ground pushes up against your feet; and when a rocket ignites its fuel behind it, the expanding exhaust gas pushes on the rocket causing it to accelerate. Download the Extramarks app now and find interesting video tutorials simplifying all the laws for you."https://www.extramarks.com/study-material/icse-class-9/physics-laws-of-motion-first-law-of-motion