Classical mechanics is the branch of physics that describes the motion of objects using Newton’s laws. It accurately predicts the behavior of everything from falling balls to orbiting satellites — and it forms the foundation of nearly all engineering on Earth. If you have ever caught a ball, driven a car, or watched a rocket … Read more
Newton’s first law states that an object stays at rest or keeps moving at constant speed in a straight line unless a net external force acts on it. This means motion does not need a cause — stopping does. This concept is called inertia, and it completely overturns the way most people intuitively think about … Read more
Newton’s second law states that the net force acting on an object equals its mass times its acceleration. In equation form: F = ma. This single equation is the mathematical engine of all classical mechanics — it lets you predict exactly how any object will move when forces act on it. If the first law … Read more
A free body diagram (FBD) is a sketch that shows every force acting on a single object as an arrow. It is the most important problem-solving skill in all of mechanics — drawing one correctly is the difference between getting the right answer and getting lost. Every physics teacher says the same thing: “Start with … Read more
Newton’s third law states that for every action force, there is an equal and opposite reaction force. When you push a wall, the wall pushes you back with the exact same force. These forces always come in pairs, they always act on different objects, and they always appear simultaneously. This law explains how rockets fly, … Read more
Friction is the force that resists the sliding, rolling, or flowing of one surface over another. It acts parallel to the contact surface and opposes relative motion between the two surfaces. Without friction, you could not walk, hold a cup, write with a pen, or stop a car. Friction is not a flaw in the … Read more
Projectile motion is the curved path an object follows when launched into the air and acted upon only by gravity. The trajectory is always a parabola (when air resistance is ignored), and the key to solving any projectile problem is treating horizontal and vertical motion as completely independent. Whether you are analyzing a basketball shot, … Read more
An inclined plane problem involves an object on a tilted surface (a ramp). The challenge is figuring out the forces acting on the object and determining whether it slides, how fast it accelerates, and what additional force might be needed to keep it still or push it up. This is a problem-solving page. If you … Read more
Work in physics is the energy transferred to an object when a force moves it through a distance. Holding a heavy suitcase while standing still is exhausting — but in physics, it counts as exactly zero work. No displacement means no work, no matter how hard you strain. This article covers the precise physics definitions … Read more
Conservation of momentum states that in an isolated system (no external forces), the total momentum before an event equals the total momentum after. This law governs every collision, every explosion, and every interaction between objects — from billiard balls to car crashes to rocket launches. Momentum is the “quantity of motion” — it combines how … Read more
Centripetal force is the net force directed toward the center of a circular path that keeps an object moving in a circle. It is not a new type of force — it is a label for whatever force (gravity, friction, tension) happens to point inward. Any object moving in a circle is accelerating, even if … Read more
Newton’s law of universal gravitation states that every object in the universe attracts every other object with a force proportional to the product of their masses and inversely proportional to the square of the distance between them. This single law explains why apples fall, why the Moon orbits, and why galaxies hold together. Gravity is … Read more
Torque is the rotational equivalent of force — it is what makes things spin, turn, and rotate. While a force causes linear acceleration, torque causes angular acceleration. If you have ever opened a door, tightened a bolt, or ridden a bicycle, you have applied torque. The key insight is that torque depends not just on … Read more
