Why does a syringe go down when you push it then pop back up again?

When you push down on a syringe plunger, you compress the air or liquid inside, creating increased pressure. Once the plunger is released, the pressure inside the syringe decreases, allowing the plunger to return to its original position due to the force of the surrounding air pressure or liquid pushing back against it. This is an example of how pressure dynamics in a closed system work, causing the plunger to pop back up.