COLLISION: ELASTIC AND INELASTIC
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| Image source: http://www.mgstech.net/wp-content/uploads/2012/10/car_crash_ah_22423.jpg |
What comes into your mind when you heard "collision" ? Have you thought of this....?? What could be the explanation of this scenario in Physics? Let's talk more about it in this article.
COLLISION
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| http://www.baltana.com/tag/collision.html |
Collision is defined as the meeting of particles or of bodies in which each exerts a force upon the other, causing the exchange of energy or momentum. As shown in the picture above, you can see two cars both having momentum and energy initially, and exchanging that energy and momentum through their interaction called collision. Now, let's try to check what's the principle behind this event.
THE PRINCIPLE...
THE LOGIC BEHIND CONSERVATION OF MOMENTUM
Consider a collision between two objects - object 1 and object 2. For such a collision, the forces acting between the two objects are equal in magnitude and opposite in direction (Newton's third law). This statement can be expressed in equation form as follows.
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| click for Newton's Third Law |
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| Relationship of time and force with impulse |
The forces act between the two objects for a given amount of time. In some cases, the time is long; in other cases the time is short. Regardless of how long the time is, it can be said that the time that the force acts upon object 1 is equal to the time that the force acts upon object 2. This is merely logical. Forces result from interactions (or contact) between two objects. If object 1 contacts object 2 for 0.050 seconds, then object 2 must be contacting object 1 for the same amount of time (0.050 seconds).
Since the forces between the two objects are equal in magnitude and opposite in direction, and since the times for which these forces act are equal in magnitude, it follows that the impulses experienced by the two objects are also equal in magnitude and opposite in direction. As an equation, this can be stated as.
But the impulse experienced by an object is equal to the change in momentum of that object (the impulse-momentum change theorem). Thus, since each object experiences equal and opposite impulses, it follows logically that they must also experience equal and opposite momentum changes. As an equation, this can be stated as
This equation is one statement of the law of momentum conservation. In a collision, the momentum change of object 1 is equal to and opposite of the momentum change of object 2. That is, the momentum lost by object 1 is equal to the momentum gained by object 2. In most collisions between two objects, one object slows down and loses momentum while the other object speeds up and gains momentum. If object 1 loses 75 units of momentum, then object 2 gains 75 units of momentum. Yet, the total momentum of the two objects (object 1 plus object 2) is the same before the collision as it is after the collision. The total momentum of the system (the collection of two objects) is conserved.
(please visit for more explanation: http://www.physicsclassroom.com/class/momentum/Lesson-2/Momentum-Conservation-Principle)
ELASTIC COLLISION
Collisions between objects are governed by laws of momentum and energy. When a collision occurs in an isolated system, the total momentum of the system of objects is conserved. Provided that there are no net external forces acting upon the objects, the momentum of all objects before the collision equals the momentum of all objects after the collision. If there are only two objects involved in the collision, then the momentum lost by one object equals the momentum gained by the other object.
Certain collisions are referred to as elastic collisions. Elastic collisions are collisions in which both momentum and kinetic energy are conserved. The total system kinetic energy before the collision equals the total system kinetic energy after the collision. If total kinetic energy is not conserved, then the collision is referred to as an inelastic collision.
(souce: http://www.physicsclassroom.com/mmedia/momentum/trece.cfm) |
| Different situations where elastic collision is observed. More details in http://www.physicstutorials.org/home/impulse-momentum/collisions |
INELASTIC COLLISION
A collision is said to be an inelastic collision, if the kinetic energy is not conserved in the collision. However, the momentum is conserved.
In these collisions the kinetic energy of the system of objects is not conserved after the collision.The resultant momentum of the bodies that are involved in the collision remains the same. In these types of collisions some of the initial kinetic energy is converted into the heat energy. This heat energy is utilized in a little deformation of the bodies or in some other work or utilized in other manner.
The collisions which tend to slow down the involved bodies or leads to them sticking together are called inelastic collisions. In these collisions some kinetic energy is utilized in the vibration of the atoms of the objects involved. The kinetic energy lost in the collision appears in the form of heat energy, sound energy or light energy. The forces of interaction in an inelastic collision are non-conservative in nature. Most of the collisions between macroscopic bodies are inelastic collisions. If a ball is dropped from a certain height and it is unable to rise to its original height, it would mean that ball has lost some kinetic energy (which would appear as heat energy). This would mean that collision is an Inelastic Collision.
See also: http://physics.tutorvista.com/momentum/inelastic-collision.html |
| Inelastic collision. see more pictures and problems at http://www.bluffton.edu/homepages/facstaff/bergerd/classes/NSC109/Handouts/answers3-2.html |
For more video tutorials, you can also check these:
https://www.youtube.com/watch?v=8ko3qy9vgLQ
https://www.youtube.com/watch?v=Xe2r6wey26E
