Momentum, Conservation of Momentum

Momentum is a vector measurement.  (Vector: Direction + speed/measurement).

It is in the same direction as velocity.

Scientists calculate momentum by multiplying the mass of the object by the velocity of the object. 

Momentum indicates how hard it would be to stop the object. 

If you were running, you might have a mass of 50 kilograms and velocity of 10 meters per second west.

Momentum calculation: mass in kilograms x velocity in meters/second

Momentum (p)=    __________________kg-m/s west

Remember Newton's First Law? It said that any object moving will continue moving unless it is interfered with. That idea applies to momentum as well. The momentum of an object will never change if it is left alone. If the 'm' (mass) value and the 'v' (velocity) value remain the same, the momentum value will be constant. The momentum of an object, or set of objects (system), remains the same if it is left alone. Within such a system, momentum is said to be conserved

Here's the momentum idea in simpler terms. When you

throw a ball at someone and it hits him hard, it hurts

because it was difficult to stop (had momentum).Think

about it. If you throw a small ball and a large ball at the

same speeds, the large ball will hit a person with a greater

momentum, be harder to stop, and hurt more. When the

mass is greater (at the same speeds), the momentum is

greater.

We already told you that the momentum of

an isolated object (or system of objects)

is conserved. If the net force acting on an

object is zero, then the linear momentum is

constant.

In an elastic collision (such as a

super ball hitting and rebounding from the

ground), no kinetic energy is lost. All of that

energy is still in the object, so we say that

energy was conserved. 

What about an inelastic collision? In

an inelastic collision, some of the energy will be lost to heat or sound or light or some other energy. The thing to remember is that the total energy didn't change, but some of it escaped into the air, ground, etc. Try throwing a piece of clay on the ground. When the clay slams into the ground, some of the kinetic energy of the clay was lost as heat and sound to the ground and air, and some of the heat remains in the clay. Since the velocity became zero, so did the momentum. The energy is still around, but divided up in different places.