Inertia is the way a body will stay still, or move, unless acted upon by any external force.
The marble that had been in rolling stops. And the one that had been still, now rolls.
The force of the rolling marble transfers to the other one. It stops the first and sets the second in motion.
Why did it happen?
* Inertia is the way one object sets another object in motion
* An object at rest tends to stay at rest. An object that is moving tends to keep moving in the same direction.
* An object stays at rest, or keeps moving , unless some external force acts upon it.
Now put two marbles on the stick so they touch and a third marble several cm away. Gently tap the single marble into the other two. Notice that the rolling maple stops, the middle one stays still and the third one rolls!
The momentum went through the second marble into the third. Try other combinations, two marbles into three, or three into three, You will find that however many marbles you set in motion, the same number will be made to roll when they are hit.