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Kinematics and dynamics

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					Kinematics and dynamics
   Elastic and Inelastic collisions




Physics colocium
   Elastics collision
Definition=
  A collision between two objects is elastic if the total
 kinetic energy of the objects is conserved, if the
 total kinetic energy of the objects before collision is
 equal to that after collision.

Eg: collisions between gas molecules
Apply law of conservation of linear
 momentum

     m1u1 + m2u2 = m1v1 + m2v2

Since the kinetic energy of the system is
 conserved:

1/2m1u1² +1/2m2u2² = 1/2m1v1²+ 1/2m2v2²
   The molecules of a gas or liquid rarely experience
    perfectly elastics collision because kinetic energy is
    exchanged between the molecules' translational motion
 Perfectly elastic collision
     Definition:
     A perfectly elastic collision is defined as one in
    which there is no loss of kinetic energy in the
    collision.
Collisions between hard spheres may be nearly
elastic, so it is useful to calculate the limiting case of
an elastic collision. The assumption of conservation
of momentum as well as the conservation of kinetic
energy makes possible the calculation of the final
velocities in two-body collisions
A popular demonstration of conservation of
momentum and conservation of energy features
several polished steel balls hung in a straight line in
contact with each other
   Inelastic collisions
Definition=
  A collision between two objects is inelastic if the
  total kinetic energy of the objects is not conserved .
Eg: A basketball rebound from the ground

   Perfectly inelastic collision
Meaning=
 A collision where two objects coalese and move with
 a common velocity
   In a perfectly inelastic collision, a zero
    coefficient of restitution, the colliding
    particles stick together. It is necessary to
    consider conservation of momentum:

             maua + mbub = (ma+mb)v



    * the reduction of kinetic energy there
    may be a transfer of kinetic energy from
    one particle to the other
The End

      Loh kha bee 6RA
      Revathy
      Fadhli

				
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