I know this will most likely be a relatively simply answer but I am currently doing some questions regarding forces acting on the piston of a syringe.
My (basic) question is, if I fill a syringe full of liquid, what is stopping the liquid in it 'falling' out (and exchanging with air)? Is it that the atmospheric pressure is acting on the plunger and the mouth of it, creating an equilibrium condition? Or that the liquid and air can't escape/interchange due to some force?
Secondly if I connect this syringe to a body of liquid, e.g. the human blood stream, what stops blood from interchanging with the liquid in the syringe. If the blood is at a higher pressure than the syringe liquid, then it would flow in? or vice versa? without moving the plunger?
Any help would be greatly appreciated!