Momentum is a baseball term. If your team has momentum in the final game of the World Series it's on a roll. Your players have a positive attitude. And unless things change, it looks like your team is going to win the series.

Momentum is also a science term. In fact, it is one of those basic concepts in physics that you cannot do without. It combines two other basic physics concepts, mass and velocity.

In physics, the symbol for momentum is the lower-case letter p, so the equation for momentum is normally written:

An object has a large momentum if its mass is large or if its velocity is large. Both mass and velocity are equally important when it comes to calculating the momentum of an object.

An interesting thing about momentum is that in a collision, momentum doesn't change. Consider what happens to the momentum when a baseball bat strikes a baseball sitting quietly on a batting tee. The bat has momentum that is based on its mass and the velocity of the swing. The ball has no momentum&emdash;it has mass but zero velocity. At the point of contact, the bat transfers some of its momentum to the baseball. The bat continues to move at a slower speed and the ball flies from the tee at a much faster speed. The momentum of the bat after the collision plus the momentum of the ball after the collision equals the momentum of the bat before the collision.

Since the mass of a bat is considerably greater than the mass of a baseball, the velocity of the ball will be much greater than the loss of velocity of the bat.

Another interesting thing about momentum is that it is a vector quantity. That means that momentum has both magnitude and direction. When a baseball bat strikes a baseball, momentum is transferred. Since momentum has both magnitude and direction the momentum that is transferred to the ball has the direction that the moving bat had. But the direction that the ball moves may not be exactly the same direction that the bat was moving.