Elastic collision with a massless box

[hdp]

Homework Statement

At one stage of my problem, I am stuck with this problem :
A block with negligible size and mass m if put in a box of no mass is situated on a horizontal plane. And the block starts moving with velocity V it would collide with the box elastically. What would be the fate of the collision.

Relevant Equations

P = mv
Momentum Conservation
Kinetic energy Conservation

Using elastic equation I think the box and the block would stich together

[Mentor Note -- Sideways, dark image fixed up]

 

[jbriggs444]

Homework Statement: At one stage of my problem, I am stuck with this problem :
A block with negligible size and mass m if put in a box of no mass is situated on a horizontal plane. And the block starts moving with velocity V it would collide with the box elastically. What would be the fate of the collision.
Relevant Equations: P = mv
Momentum Conservation
Kinetic energy Conservation

Using elastic equation I think the box and the block would stich together

What is the energy of a moving massless box?
What is the momentum of a moving massless box?
Do either depend on the velocity of the moving massless box?
So can we ever deduce anything about the velocity of the massless box?

 

[kuruman]

Can you post the statement of the problem as was given to you? I don't understand what "fate of the collision" means. From what you have told us, the only relevant equation here is $$0=0.$$

 

[haruspex]

The reliable way to analyse idealised problems, such as zero mass, is to analyse the realistic version first then take the limit as the ideal is approached.
(With more than one idealisation the order of taking limits can change the answer.)
Giving the larger box mass M, what equations can you write?

 

[Steve4Physics]

Homework Statement: At one stage of my problem, I am stuck with this problem :
A block with negligible size and mass m if put in a box of no mass is situated on a horizontal plane. And the block starts moving with velocity V it would collide with the box elastically. What would be the fate of the collision.

Zero mass for the box sounds unphysical. However, you can get a (probably reasonable) intuition if you consider the case where the box’s mass is negligible compared to the block’s mass.

Where is the system's centre of mass?

Have you learnt about elastic collisions in the centre of mass frame? What events would an observer at the centre of mass see?

By the way, did you resolve your question “How to assign signs to energy?” (in the thread https://www.physicsforums.com/threads/how-to-assign-signs-to-energy.1059533/)?

Edit: typo's

 

[haruspex]

@hdp, did you try the approach in post #4? The result is very surprising.