by on September 18, 2020
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Elastic collision

 

Elastic collision is a type of collision in which both energy and momentum are conserved.

There is no loss of energy , neither loss of momentum in elastic collision.

Example of elastic collision are ;

  1. A ball that bounces off the ground back to the original height.
  2. Molecules of gases in a container , hit the wall of the container and bounces back.

The momentum and kinetic energy remain the same after the collision.

Momentum = mass x velocity

MV + mv = MU + mu = constant

where V ,v and U, u are the initial and final velocities respectively.     For an Elastic collision the momentum is conserved

  

 

 

If a ball bounces back from the ground

Total moment before collision= MV + mv= M x 0  + m x v= mv where the initial  velocity of the ground=0

Total momentum after collision = MU + mu= M X0 + m x u = mu

Hence mv =mu,  v=u

The Total kinetic energy before collision =  and after collision , the total kinetic energy = , hence,    

v=u

 

Inelastic collision

Inelastic collision is a type of collision in which only the momentum is conserved.

There is  loss of energy  in inelastic collision.

Example of inelastic collision are ;

  1. A lorry and a car that collide with each other.
  2. An aeroplane that crashes to the ground.

The momentum  remain the same after the collision, but there is loss of kinetic energy.

The momentum before collision = MV + mv

The momentum after collision = MU + mu

 

MV + mv = MU + mu .  if they move together after collision with common velocity u

Then

 MV + mv = (M + m)u

where V ,v and U, u are the initial and final velocities respectively.     For an inelastic collision the momentum is conserved but the K.E is not.

 

  

 

    because U and u are less than V and v respectively

if they move together and  have common velocity u after collision, then

 

Read more about PHYSICS for High Schools

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