Chapter 7
Linear Momentum and Collisions
By Boundless
![Thumbnail](../../../../../figures.boundless-cdn.com/16971/square/ns-cradle-animation-book-2.gif)
Linear momentum is the product of the mass and velocity of an object, it is conserved in elastic and inelastic collisions.
![Thumbnail](../../../../../figures.boundless-cdn.com/16972/square/billard.jpeg)
In the most general form, Newton's 2nd law can be written as
![Thumbnail](../../../../../figures.boundless-cdn.com/16973/square/figure-09-02-01a.jpeg)
Impulse, or change in momentum, equals the average net external force multiplied by the time this force acts.
![Thumbnail](../../../../../figures.boundless-cdn.com/30714/square/figure-09-06-03a.jpeg)
In an inelastic collision the total kinetic energy after the collision is not equal to the total kinetic energy before the collision.
![Thumbnail](../../../../../figures.boundless-cdn.com/18424/square/deflection.jpg)
Glancing collision is a collision that takes place under a small angle, with the incident body being nearly parallel to the surface.
![Thumbnail](../../../../../figures.boundless-cdn.com/17234/square/elastischer-sto-c3-9f3.gif)
An elastic collision is a collision between two or more bodies in which kinetic energy is conserved.
![Thumbnail](../../../../../figures.boundless-cdn.com/17235/square/figure-09-06-02a.jpeg)
To solve a two dimensional elastic collision problem, decompose the velocity components of the masses along perpendicular axes.
![Thumbnail](../../../../../figures.boundless-cdn.com/17237/square/inelastischer-sto-c3-9f.gif)
Collisions may be classified as either inelastic or elastic collisions based on how energy is conserved in the collision.
![Thumbnail](../../../../../figures.boundless-cdn.com/17238/square/figure-09-06-03a.jpeg)
While inelastic collisions may not conserve total kinetic energy, they do conserve total momentum.
![Thumbnail](../../../../../figures.boundless-cdn.com/12988/raw/center-gravity-2.jpg)
The position of COM is mass weighted average of the positions of particles. Mathematically, it is given as
![Thumbnail](../../../../../figures.boundless-cdn.com/17154/square/orbit3.gif)
We can describe the translational motion of a rigid body as if it is a point particle with the total mass located at the COM—center of mass.
![Thumbnail](../../../../../figures.boundless-cdn.com/30772/square/-vinci-vitruve-luc-viatour.jpeg)
The center of mass (COM) is an important physical concept—it is the point about which objects rotate.
![Thumbnail](../../../../../figures.boundless-cdn.com/17152/square/1.jpeg)
The COM (center of mass) of a system of particles is a geometric point that assumes all the mass and external force(s) during motion.