Question

1. In addition to numerical problems, such as number 8, you should be able to answer questions based on quantitative or qualitative reasoning. Your answer should be based on physics principles and definitions, as well. Answer the following by invoking physics principles and definitions to deduce various results:
   1. Why must an IV bag be placed above a patient’s arm, but a syringe can be applied horizontally?
   2. Where in the circulatory system would you expect the blood pressure to be highest?
   3. Water flows in a horizontal pipe that has no branching. Suppose this pipe were replaced by another pipe with one-tenth the diameter, where the length and flow rate were not changed. How would this affect the pressure drop across the entire pipe?
   4. A water bottle has a small hole somewhere along the side. However, the water only comes out if the bottle cap has been removed, but does not come out if the bottle cap is on tight. Explain.

Answer 1

A) The IV bag must be placed above the patient's arm but a syringe applied horizontally because IV does not have internal pressure whereas the syringe has high internal pressure.

B) Heart is the organ that is responsible to pump the blood, so as soon as the pure blood moves out form heart through aorta the blood pressure is highest

C) We know, P=F/A, i.e. the pressure is inversely proposnate the area of cross-section. If the area of the pipe is reduced to one-tenth than the pressure will increase ten times.

D) The reason behind this is that, when the cap of the bottle is on that pressure inside and outside the bottle remains same whereas when the bottle cap is opened than due to pressure difference water starts flowing out of the bottle.