Elastic and Inelastic collisions - Question. (1 Viewer)

[~shinigami~]

How would I show, using formulae and such to show that a collision is elastic or inelastic?

I know that an elastic collision conserves Kenetic Energy so would it be something like this:

½m₁u₁² + ½m₂u₂² = ½m₁v₁² + ½m₂v₂²

Thank You in advance.

 

[BigBear_25]

How would I show, using formulae and such to show that a collision is elastic or inelastic?

I know that an elastic collision conserves Kenetic Energy so would it be something like this:

½m₁u₁² + ½m₂u₂² = ½m₁v₁² + ½m₂v₂²

Thank You in advance.

Well your right for the elastic collisions part the formula is right.
For inelastic collision you would have something similar:



½m₁u₁² + ½m₂u₂² = ½m₁v₁² + ½m₂v₂² + energy loss

I think this is how you do it. Its been a while since i have done this.

Hope is helps.

 

[~shinigami~]

Thank You Big Bear for confirming the elastic collision formula and thank you for showing me the inelastic formula.

Also for inelastic, can I just use the elastic formula and show that initial KE does not equal final KE therefore inelastic?

 

[rama_v]

In completely inelastic collisions, the masses stick together.
So the equation for momentum becomes

m₁u₁+ m₂u₂= (m₁+m₂)v

This page is useful
http://hyperphysics.phy-astr.gsu.edu/hbase/inecol.html#c1

EDIT: equation changed. thanks zeropoint (read below)

 

[~shinigami~]

Thanks for the reply and link rama V.

 

[zeropoint]

In completely inelastic collisions, the masses stick together.
So the equation becomes

½m₁u₁² + ½m₂u₂² = ½(m₁+m₂)v²

This page is useful
http://hyperphysics.phy-astr.gsu.edu/hbase/inecol.html#c1

This equation is wrong. I think what you meant to say was that

m₁u₁ + m₂u₂ = (m₁+m₂)v

Kinetic energy is not conserved in an inelastic collision, whereas momentum is always conserved.

 

[rama_v]

This equation is wrong. I think what you meant to say was that

m₁u₁ + m₂u₂ = (m₁+m₂)v

Kinetic energy is not conserved in an inelastic collision, whereas momentum is always conserved.

Oh oops yeah you are right. kinetic energy is not conserved but momentum is. Oh and I think momentum is ONLY conserved when the external forces on a system are negligeable, right?

 

[~shinigami~]

So is the formula I wrote at the top still right?

 

[rama_v]

So is the formula I wrote at the top still right?

Yeah your one is correct. My original is incorrect.

 

[~shinigami~]

Thanks for confirming that rama.

I was getting worried about using the wrong formula.