Question

1) When a patient receives an injection, fluid passes from a cylinder with a plunger in it, through a narrow, hollow needle, and into the patient’s arm.

a. Why will fluid travel more rapidly through the needle if the nurse squeezes harder on the plunger?

b. As the fluid flows out of the needle and slows down in the patient’s tissue, what happens to its pressure?

c. Why doesn’t the blood flow back out of the vein when the needle is removed?

2) A traditional water cooler has a large bottle of water turned upside down so that its neck is submerged in a small chilled water reservoir at the top of the water cooler. The water level in the small reservoir remains just above the neck of the bottle. If you open the valve to let water out of the reservoir, bubbles of air rise up into the water bottle and the level of water in the bottle goes down.

a. Since there is no true seal between the neck of the bottle and the reservoir, what holds the water up inside the water bottle?

Answer 1

1)

(a) Because extra force by the nurse will cause the fluid to travel quicker through the body.

(b) It is less pressure than when the nurse was applying force to the plunger to squeeze the fluid through the needle and into the blood stream.

(c) Because the needle is being pushed in and not being pulled so blood does not flow back out of the vein.

2)

(a) The pressure inside the bottle is uniformed which mean that each portion of the water feels no net force, which in turn cause it not to accelerate.