What do 'perfect elastic' and 'perfect inellastic' collision mean?

In summary: In an elastic collision, kinetic energy is conserved. In an inelastic collision, some of the kinetic energy is transformed in other forms of energy (usually heat).
  • #1
kthouz
193
0
What does mean a perfect elastic collision and a perfect inellastic collision? Do they really exist or it is just by assuming?
 
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  • #2
In an elastic collision kinetic energy is conserved. In an inelastic collision the two colliding things form a new unique object (they stay glued together), and some of the kinetic energy is transformed in other forms of energy (usually heat).

Perfectly elastic collisions exist, but not with macroscopic objects. There is always some energy lost to noise and heat. But at particle level (molecules, atoms, electrons, etc.) most of the collisions are perfectly elastic.
 
  • #3
conservative force.

How to find mathematically that a force is conservetive? i know by definition that a conservative force is a force in which work done is indipendent of the path followed like gravitational force.
 
  • #4
if we know the function of the force , and [tex]\nabla \times F=0[/tex]

then it is conservetive
 
  • #5
but i don't know, kthouz,whether you are a college student.

if not, just remember the friction isn't
 
  • #6
enricfemi said:
if we know the function of the force , and [tex]\nabla \times F=0[/tex]

then it is conservetive

What about

[tex]F \left( x , y , z \right) = \frac{-y}{x^2 + y^2} \hat{x} + \frac{x}{x^2 + y^2} \hat{y}?[/tex]

:uhh:
 
  • #7
George Jones said:
What about

[tex]F \left( x , y , z \right) = \frac{-y}{x^2 + y^2} \hat{x} + \frac{x}{x^2 + y^2} \hat{y}?[/tex]

:uhh:

What about [tex] x=y=0[/tex]?

[tex]\nabla\times F= 0[/tex] except for [tex] x=y=0[/tex]

The function has a discontinuity for [tex] x=y=0,\,\,\, F=\infty[/tex]
For any closed path that does not enclose the origin, any line integral of the function is zero.

Happily, in physics you don't often find functions with poles.

Anyhow, I don't think that this thread is the good one to talk about curls and discontinuities.

It is better to stick to the original question and to the level of the question. Talk about curls to someone who asks about elastic collisions is not a good idea. There are other ways to explain what is a conservative force.
 
  • #8
alright,alright, so talk about how to explain conservetive force mathematically
without curls.
 
  • #9
This is a physics forum. In physics you do not need mathematics to explain anything. You explain without math and, once it has been understood, you use the math to calculate.

I can assure you that, in physics if you need math to explain something, it means that you have not well understood the subject.

A conservative force is a force whose exerted work is converted in potential energy which can be transformed back completely into mechanical work.
 

What does "perfect elastic collision" mean?

A perfect elastic collision is a type of collision where the kinetic energy of the system is conserved. This means that the total kinetic energy before the collision is equal to the total kinetic energy after the collision.

What does "perfect inelastic collision" mean?

A perfect inelastic collision is a type of collision where the kinetic energy of the system is not conserved. This means that some of the kinetic energy is lost during the collision and is converted into other forms of energy, such as heat or sound.

What factors affect the elasticity of a collision?

The elasticity of a collision is affected by the nature of the objects colliding, their masses, and the materials they are made of. The elasticity is also affected by the speed and angle at which the objects collide.

What is an example of a perfect elastic collision?

An example of a perfect elastic collision is the collision of two billiard balls on a pool table. The total kinetic energy of the system (the two balls) remains the same before and after the collision.

What is an example of a perfect inelastic collision?

An example of a perfect inelastic collision is when a car crashes into a wall. The kinetic energy of the car is converted into other forms of energy, such as sound and heat, and the total kinetic energy of the system (the car and the wall) is not conserved.

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