kinematics - Inertia Vs Momentum - Physics Stack Exchange
The impulse-momentum theorem states that the change in momentum of an object equals the impulse applied to it. The impulse-momentum theorem is logically equivalent to Newton's second law of motion (the force law). 1st law, inertia. To distinguish between inertia and momentum and why one is used in momentum of a system cannot be changed unless an external force. Inertia, Momentum, Impulse, and Kinetic Energy. Forces change an object's motion, but without them, an object will keep doing whatever it was doing.
Shortly before Galileo's theory of inertia, Giambattista Benedetti modified the growing theory of impetus to involve linear motion alone: Classical inertia[ edit ] Galileo Galilei The principle of inertia which originated with Aristotle for "motions in a void" states that an object tends to resist a change in motion.
How it works - Momentum - Momentum and Inertia, Mass and Weight, Velocity and Speed
According to Newton, an object will stay at rest or stay in motion i. The Aristotelian division of motion into mundane and celestial became increasingly problematic in the face of the conclusions of Nicolaus Copernicus in the 16th century, who argued that the earth and everything on it was in fact never "at rest", but was actually in constant motion around the sun. A body moving on a level surface will continue in the same direction at a constant speed unless disturbed.
The first physicist to completely break away from the Aristotelian model of motion was Isaac Beeckman in Unless acted upon by a net unbalanced force, an object will maintain a constant velocity.
- Impulse & Momentum
- Inertia and Mass
- Inertia, Momentum, Impulse, and Kinetic Energy
Note that "velocity" in this context is defined as a vectorthus Newton's "constant velocity" implies both constant speed and constant direction and also includes the case of zero speed, or no motion.
Since initial publication, Newton's Laws of Motion and by inclusion, this first law have come to form the basis for the branch of physics known as classical mechanics.
Kepler defined inertia only in terms of a resistance to movement, once again based on the presumption that rest was a natural state which did not need explanation. It was not until the later work of Galileo and Newton unified rest and motion in one principle that the term "inertia" could be applied to these concepts as it is today.
In fact, Newton originally viewed the phenomenon he described in his First Law of Motion as being caused by "innate forces" inherent in matter, which resisted any acceleration. Given this perspective, and borrowing from Kepler, Newton attributed the term "inertia" to mean "the innate force possessed by an object which resists changes in motion"; thus, Newton defined "inertia" to mean the cause of the phenomenon, rather than the phenomenon itself.
Momentum - How it works
However, Newton's original ideas of "innate resistive force" were ultimately problematic for a variety of reasons, and thus most physicists no longer think in these terms. In physics, we quickly learn the the only difference between an object moving or being at rest is the relative motion of the observer, so both of these cases are really the same thing.
Inertia simply tells us that to change the motion of an object requires applying a force to it. To fully describe the property of Inertia with units we can measure, we must quantify an object's speed of motion, direction of motion, and resistance to change of motion.
We combine these three things into a single parameter for each object called its Momentum.
The resistance to change of motion does not depend upon direction, so it is what we call a "scalar" quantity, and has been named Mass. We quantify Mass using units such as kg or lb-mass. Objects that require a lot of Force to accelerate a little bit have large Mass.
What are momentum and impulse?
Objects that accelerate a lot with a little bit of Force have small Mass. Galileo postulated that if friction could be entirely eliminated, then the ball would reach exactly the same height. Galileo further observed that regardless of the angle at which the planes were oriented, the final height was almost always equal to the initial height.
If the slope of the opposite incline were reduced, then the ball would roll a further distance in order to reach that original height. Galileo's reasoning continued - if the opposite incline were elevated at nearly a 0-degree angle, then the ball would roll almost forever in an effort to reach the original height.
Impulse & Momentum - Summary – The Physics Hypertextbook
And if the opposing incline was not even inclined at all that is, if it were oriented along the horizontalthen Newton's first law of motion declares that a force is not needed to keep an object in motion. Slide a book across a table and watch it slide to a rest position. The book in motion on the table top does not come to a rest position because of the absence of a force; rather it is the presence of a force - that force being the force of friction - that brings the book to a rest position.
In the absence of a force of friction, the book would continue in motion with the same speed and direction - forever! Or at least to the end of the table top. A force is not required to keep a moving book in motion.
In actuality, it is a force that brings the book to rest. Mass as a Measure of the Amount of Inertia All objects resist changes in their state of motion. All objects have this tendency - they have inertia.