Question 15

[hoanle888753]

I thought decreasing the diameter and thus the radius of the blood vessel would decrease resistance. Why isn't choice C correct?

[mcat_premed3832]

I once had a teacher that made the following analogy about resistance:

2 hallways with the same density of students in each: let's say you needed to run from one end of the hallway to another, would you encounter more or less resistance with a wide hallway? Consider your answer.

A wide hallway gives you more options to avoid other students and so you can get through much faster. Increased diameter therefore reduces resistance.

In fact, you should be able to say specifically by how much! The reason is because the inverse square relationship between resistance and radius is on the official Gold Standard Physics Equation List: www.goldstandard-mcat.com/physics-equation-lists/