Unit 7 Post - 7/05: Conservation of Momentum

In systems involving force, velocities, and momenta; the basic concept to be understood is that velocities can be changed (usually transferred) but momentum is the same. Mass plays a significant role in this because momentum is the vector product of mass and velocity - so the greater the mass the greater the momentum. Velocity is generally transferred from one object to another when they come in contact with each other and equal masses; but if they don't they transfer velocities in proportion to the differences of their masses.  But all in all, momentum is conserved, the amount that is put into the system is the amount that will come out as well - regardless of a change in mass or velocity.

 

http://webpages.uah.edu/~wilderd/resources.html

This picture demonstrates the simple concept. The two balls have the same mass so their velocities will be transferred equally. So when the white ball hits the yellow ball, the yellow ball will move with the same force that it was hit - while the white ball will sit still because that's the velocity it was hit at (when you hit something... that something hits you just as hard). The momentum of the entire reaction stays the same even though the velocities are transferred. 

http://www.russbrown.com/motorcycle-lawyer-blog/dls/car-hits-bike-300x196.jpg

This tragic picture is a real-life application of this concept. The car and the bicycle hit each other with the same amount of force and the amount of momentum in the collision remains constant. However, mass of the motorcycle is much less than that of the car, thus the motorcycle felt much more of the force while the car did not (more mass = more inertia = requires more force to accelerate), leaving the motorcycle in ruins.