Momentum
Momentum is a force associated with moving objects.
When objects move, they do so with a certain amount of energy – this is essentially what momentum is.
Momentum is the product of the mass and velocity of an object (P = mv).
So, for two objects that are the same mass, the object moving at a higher speed has more velocity, and, therefore, more “energy of motion.”
For two objects traveling the same speed, the object with the higher mass has the higher momentum.
Think about it like this – which object is harder to stop, a baseball flying through the air at 20 m/h, or a baseball traveling at 100 mi/h?
Sometimes, objects in motion collide.
When they do, some interesting things happen to those objects, and their momentum.
In one type of collision, called an inelastic collision, objects that collide stick together. When they do, their masses combine. Their velocity does not, however increase…the object moves more slowly in the direction of the greater force.
In another type of collision, called an elastic collision, objects bounce off one another. In this case, the objects affect one another’s direction, but no momentum is lost. Some momentum may, in fact, be transferred to another object (from the object with greater momentum to lower).
The simulation below shows elastic collisions. Adjust the overall mass of one of the spheres and observe the interaction between the two.
On important concept to know here is that, regardles of the type of collision two objects may have with one another, no momentum is lost in the transaction.
The Law of Conservation of Moentum says that the amount of momentum at the beginning and end of a collision will be the same.
A useful analogy for understanding momentum conservation involves a money transaction between two people. Let’s refer to the two people as Jack and Jill. Suppose that we were to check the pockets of Jack and Jill before and after the money transaction in order to determine the amount of money which each possesses. Prior to the transaction, Jack possesses $100 and Jill possesses $100. The total amount of money of the two people before the transaction is $200. During the transaction, Jack pays Jill $50 for the given item being bought. There is a transfer of $50 from Jack’s pocket to Jill’s pocket. Jack has lost $50 and Jill has gained $50. The money lost by Jack is equal to the money gained by Jill. After the transaction, Jack now has $50 in his pocket and Jill has $150 in her pocket. Yet, the total amount of money of the two people after the transaction is $200. The total amount of money (Jack’s money plus Jill’s money) before the transaction is equal to the total amount of money after the transaction. It could be said that the total amount of money of the system (the collection of two people) is conserved. It is the same before as it is after the transaction.
A good visual example of this is a Newton’s Cradle (below). When the first sphere makes contact with the spheres at rest, its momentum is transferred through the line of spheres. While the first sphere loses all of its momentum (and stops), the last sphere takes it on, and moves in a similar fashion to the first prior to the collision.
Tags: Conservation, Momentum, Newton's Third Law, Physics & Physical Science
Posted in Forces & Motion, Physics & Physical Science
