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Momentum BasicsMomentum is another vector measurement. Scientists calculate momentum by multiplying the mass of the object by the velocity of the object. It is the amount of motion you can find in an object. If you were running you might have a mass of 50 kilograms and a speed of 10 meters per second (really fast). Your momentum would be 500 kgm/sec. Easy as pi.Remember Newton's First Law? It said that any object moving will continue moving. That idea applies to momentum as well. The momentum of an object will never change if it is left alone. If the 'm' value and the 'v' value remain the same, the momentum value will be constant. Momentum is also one of those concepts in physics that is conserved. 
Here's the momentum idea in simpler terms. When you throw a ball at someone and it hits him hard, it hurts because of the 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 larger energy. When the mass is greater (at the same speeds), the momentum is greater.
A bullet is an example of an object with a very small mass moving very quickly. Bullets have very large amounts of momentum because of their high velocity. Types of Momentum
There are different types of momentum. We've been talking about linear momentum. That's when an object is moving in a straight line. With linear momentum, the momentum is in the same direction that the object is moving. If you move right, so does your momentum.
There is another type called angular momentum. Angular momentum can be found when you're not moving in a straight line. Maybe you're moving in a circle. If you tie a ball to a string and spin it, there is still momentum, but now it's in a direction perpendicular (a right angle, 90 degrees off) to the direction of your velocity. 
Conserving MomentumWe already told you that momentum is conserved. If the force acting on an object is zero, then the linear momentum is constant. In an elastic collision (such as a rubber ball hitting the ground), no kinetic energy is lost. All of that energy is still in the object. If all of the energy stays in the object, the momentum doesn't change. Both values stay the same.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 all of the energy is still there; it has just been transformed into a new thing. That new thing is no longer momentum because something acted on your object and the momentum was transformed. The total energy is still conserved. Try throwing a piece of clay on the ground. When the clay slams into the ground, the energy of momentum was lost from the clay (because the velocity became zero) and transferred to the ground. The energy is still around, just in a different place. 
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Go for site help or list of physics topics at the site map!©copyright 1997-2007 Andrew Rader Studios, All rights reserved. Current Page: Physics4Kids.com | Motion | Momentum |
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