NTNUJAVA Virtual Physics Laboratory
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Easy Java Simulations (2001- ) => dynamics => Topic started by: ahmedelshfie on April 27, 2010, 09:03:14 pm



Title: Elastic collision and in-elastic collision
Post by: ahmedelshfie on April 27, 2010, 09:03:14 pm
This applet created by prof Hwang
Modified by Ahmed
Original project Elastic collision and in-elastic collision (http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1122.0)

This simulation use a spring to simulate the process during collision for elastic and in-elastic collision.
The spring will be compressed when two objects collide with each other.
The spring will return back to it's original length for elastic collision.
However, the spring will keep at the largest compression (when both objects are the same speed), and both objects will move with the same speed later on.

The green curve show the sum of the kinetic energy for both objects, i.e. (1/2)m1*v12+(1/2)m2v22
The sum of two kinetic energy become smaller during collision, because some of the energy goes to potential energy of the spring. The energy will be released back when the collision is finished.
However, the energy will be loss during in-elastic collision.

The blue curve and gray curve are velocity curves for both objects.
You are welcomed to check out if the total momentum is conserved or not!


Title: Re: Elastic collision and in-elastic collision
Post by: ahmedelshfie on April 27, 2010, 11:20:49 pm
An elastic collision is an encounter between two bodies in which the total kinetic energy of the two bodies after the encounter is equal to their total kinetic energy before the encounter. Elastic collisions occur only if there is no net conversion of kinetic energy into other forms. This definition applies to close encounters between a spacecraft and a gravitating body ( see gravity assist) as well as to actual collisions between individual atoms etc.

During the collision of small objects, kinetic energy is first converted to potential energy associated with a repulsive force between the particles (when the particles move against this force, i.e. the angle between the force and the relative velocity is obtuse), then this potential energy is converted back to kinetic energy (when the particles move with this force, i.e. the angle between the force and the relative velocity is acute).

The collisions of atoms are elastic collisions (Rutherford backscattering is one example).

The molecules—as distinct from atoms—of a gas or liquid rarely experience perfectly elastic collisions because kinetic energy is exchanged between the molecules’ translational motion and their internal degrees of freedom with each collision. At any one instant, half the collisions are, to a varying extent, inelastic collisions (the pair possesses less kinetic energy in their translational motions after the collision than before), and half could be described as “super-elastic” (possessing more kinetic energy after the collision than before). Averaged across the entire sample, molecular collisions can be regarded as essentially elastic as long as black-body photons are not permitted to carry away energy from the system.

In the case of macroscopic bodies, elastic collisions (except for near encounters with a gravtating body) are an ideal never fully realized, but approximated by the interactions of objects such as billiard balls.

When considering energies, possible rotational energy before and/or after a collision may also play a role.


Title: Re: Elastic collision and in-elastic collision
Post by: ahmedelshfie on April 27, 2010, 11:22:51 pm
Data and images from  http://en.wikipedia.org/wiki/Elastic_collision