Hello, 
I'm a beginner in Solidworks.
I'm accelerating a block on a rail-mounted cart using a linear motor.
When the block moves, the cart should move in the opposite direction. The calculation is correct up to this point.

Regardless of the block's mass, the cart always moves at the same speed.
This violates the law of conservation of momentum.
I've noticed that Solidworks' motion analysis doesn't yield results based on the principles of conservation of momentum.
I can't figure out where I'm making a mistake.
I would appreciate your help.
LINK: 

Orange is rail,
Gray is Cart,
Red is Block.
When block moves right with any speed, cart moves to left.
But if I change the mass of block velocity of cart remains same.