Elastic Collision: Momentum or Energy?

In summary, an elastic collision is defined as one where the kinetic energy and internal energy of the colliding objects are conserved. While momentum is conserved in any collision, it is the conservation of energy that determines whether a collision is elastic or inelastic. In order to determine if a collision is elastic, you may need to find the energy separately in addition to checking for momentum conservation. Further information on inelastic collisions can be found by researching Newton's Law of Restitution.
  • #1
Physics is Phun
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Is elastic collision defined as a collision where no energy is lost or where no momentum is lost? We had to do a lab in class and one question was whether the collison was elastic. I think we all got it wrong because we sayed it was elastic because momentum was conserved. But we were supposed to check if energy was (apparently it wasn't) conserved. (It seems kind of stupid because nowhere in the lab did we have to find the energy so we would have to find it separately to find whether it was elastic or not.) So is elasticity defined by momentum or energy?
 
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  • #2
An elastic collision is one in which the kinetic energy is conserved. Momentum is conserved in any collision, whether elastic or inelastic.
 
  • #3
An elastic collision is one in which the internal energy of the colliding objects remains unchanged meaning that the translational plus rotational energy of both objects is conserved.

Also, you were in fact asked in the lab to find the energy when the question of whether the collision is elastic was raised. :-)
 
  • #4
If you want to know more about inelastic collision, I suggest you look up on Newton's Law of Restitution.
 

FAQ: Elastic Collision: Momentum or Energy?

How is momentum conserved in an elastic collision?

In an elastic collision, the total momentum of the system before the collision is equal to the total momentum after the collision. This is because no external forces act on the system during the collision, so the total momentum remains constant.

Is kinetic energy conserved in an elastic collision?

Yes, in an elastic collision, the total kinetic energy of the system before the collision is equal to the total kinetic energy after the collision. This is because in an elastic collision, there is no energy lost to other forms, such as heat or sound.

How do you calculate the velocities of objects after an elastic collision?

The velocities of objects after an elastic collision can be calculated using the conservation of momentum and the conservation of kinetic energy equations. These equations take into account the masses and velocities of the objects before and after the collision.

Can an elastic collision occur between two objects of different masses?

Yes, an elastic collision can occur between objects of different masses. The conservation of momentum and conservation of kinetic energy equations take into account the masses of the objects, so the velocities of the objects after the collision will depend on their respective masses.

What is the difference between an elastic collision and an inelastic collision?

In an elastic collision, both momentum and kinetic energy are conserved. However, in an inelastic collision, only momentum is conserved while some kinetic energy is lost to other forms, such as heat or sound. This means that in an inelastic collision, the objects may stick together or change shape, whereas in an elastic collision they will bounce off each other with no change in shape.

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