Newton's Laws of Motion
The foundational mechanics that govern how forces control physical objects.
Formulated by Sir Isaac Newton in his 1687 masterwork 'Principia', the three laws of motion describe the exact relationship between the forces acting on a body and the motion of that body.
Whether launching rockets into space or analyzing planetary orbits, Newton's laws are the mathematical building blocks used to calculate speed, acceleration, and force vectors.
Key Takeaways
- •First Law (Inertia): An object remains in its state of rest or uniform motion unless acted upon by a net external force.
- •Second Law (F=ma): Acceleration is directly proportional to net force and inversely proportional to mass.
- •Third Law (Action-Reaction): For every action, there is an equal and opposite reaction.
Core Concepts & Definitions
1The Principle of Inertia
Inertia is the natural tendency of an object to resist changes to its state of motion. Mass is a quantitative measure of this inertia.
•An object does not require force to keep moving; it only requires force to change speed or direction.
•Friction and air resistance are the common external forces that slow objects down.
2Action-Reaction Pairs
Forces always occur in matched pairs. When you push against an object, it pushes back against you with the exact same magnitude of force in the opposite direction.
•These force pairs act on two DIFFERENT objects, which is why they do not cancel each other out.
•Rockets generate thrust because the expanding gas pushed out the nozzle pushes back against the rocket frame.
Equations & Calculation Methods
Newton's Second Law Formula
Net Force (F) acting on a body is equal to its mass (m) multiplied by its acceleration (a).
Weight Force Formula
Calculates the gravitational force acting on a mass on Earth, where g is approximately 9.81 m/s².