System of 4 Pendulums: Why Don't They Move Faster?

[teken894]

In a system of 4 same-mass pendulums, when give potential energy to a pendulum (by raising it) and letting go, one pendulum on the other side moves equally...

When two are raised and let go, two pendulums will move after the collision...

why doesn't one pendulum move with twice the speed, rather than two pendulums moving?

Isn't it that two pendulums moving slower is the same as one pendulum moving faster?Hope I have made my wording sufficiently clear...

That's the kind of system I'm referring to

 

[Tide]

It is not possible to conserve both momentum and energy if only one mass moves after the collision.

Suppose the two masses arrive with speed v and the single mass leaves with speed u. Then momentum conservation requires 2v = u but energy conservation requires $u^2 = 2 v^2$ which is possible only if v = 0 or 1 = 2.