Momentum is a fundamental concept in classical mechanics that describes the quantity of motion possessed by an object. It is defined as the product of an object’s mass and its velocity and is a vector quantity, meaning it has both magnitude and direction.
The momentum of an object is directly proportional to both its mass and its velocity. The more massive an object is, and the faster it is moving, the greater its momentum will be. Conversely, an object at rest has zero momentum, as it has no motion.
Momentum is a conserved quantity, meaning that the total momentum of a closed system (one not affected by external forces) cannot change. This is a fundamental law of physics known as the conservation of momentum. If one object in a system gains momentum, another must lose an equal amount, so that the total momentum remains constant.
The conservation of momentum has important implications. It explains why colliding objects rebound, why rockets are able to launch into space, and why the center of mass of a system continues moving at a constant velocity if no external forces act on it. It is a powerful tool for analyzing the motion of systems, from subatomic particles to galaxies.
Momentum can be changed by the application of an unbalanced force over a period of time. This relationship is described by the impulse-momentum theorem, which states that the change in an object’s momentum is equal to the impulse (force × time) applied to it. Applying a large force for a short time, or a smaller force for a longer time, can both result in the same change in momentum.
The concept of momentum is crucial in understanding collisions and impacts. In an elastic collision, where objects rebound with the same speed as before the collision, the total momentum is conserved. In inelastic collisions, where the objects stick together or deform, some momentum is lost to other forms of energy, such as heat. Understanding momentum is key to analyzing the outcomes of various types of collisions.
In summary, momentum is a fundamental property of moving objects that describes their quantity of motion. It is a conserved quantity, meaning the total momentum of a closed system remains constant. Momentum can be changed through the application of force over time, and understanding momentum is essential for analyzing the dynamics of collisions and other mechanical systems.
- Momentum – Wikipedia
The Wikipedia page on “Momentum” provides a comprehensive overview of the concept. It defines momentum as the product of an object’s mass and its velocity and discusses its significance in physics. The page also includes references to further resources on the topic. - Momentum (technical analysis) – Wikipedia
The “Momentum (technical analysis)” Wikipedia page discusses the use of momentum indicators, such as MTM and ROC, in financial technical analysis. It explains how these indicators are used to identify the strength of a price trend and provide interpretations for their signals in trading.
In Newtonian mechanics, momentum (pl.: momenta or momentums; more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If m is an object's mass and v is its velocity (also a vector quantity), then the object's momentum p (from Latin pellere "push, drive") is:
| Momentum | |
|---|---|
 Momentum of a pool cue ball is transferred to the racked balls after collision. | |
Common symbols | p, p |
| SI unit | kg⋅m/s |
Other units | slug⋅ft/s |
| Conserved? | Yes |
| Dimension | MLT−1 |
In the International System of Units (SI), the unit of measurement of momentum is the kilogram metre per second (kg⋅m/s), which is equivalent to the newton-second.
Newton's second law of motion states that the rate of change of a body's momentum is equal to the net force acting on it. Momentum depends on the frame of reference, but in any inertial frame it is a conserved quantity, meaning that if a closed system is not affected by external forces, its total linear momentum does not change. Momentum is also conserved in special relativity (with a modified formula) and, in a modified form, in electrodynamics, quantum mechanics, quantum field theory, and general relativity. It is an expression of one of the fundamental symmetries of space and time: translational symmetry.
Advanced formulations of classical mechanics, Lagrangian and Hamiltonian mechanics, allow one to choose coordinate systems that incorporate symmetries and constraints. In these systems the conserved quantity is generalized momentum, and in general this is different from the kinetic momentum defined above. The concept of generalized momentum is carried over into quantum mechanics, where it becomes an operator on a wave function. The momentum and position operators are related by the Heisenberg uncertainty principle.
In continuous systems such as electromagnetic fields, fluid dynamics and deformable bodies, a momentum density can be defined, and a continuum version of the conservation of momentum leads to equations such as the Navier–Stokes equations for fluids or the Cauchy momentum equation for deformable solids or fluids.