An artery is constricted at one location to 1/2 its normal cross-sectional area.
how does the speed of blood past the constriction compare to the speed of blood flow in the rest of the artery? (note: assume ideal fluid flow.)

a) it is 1/4 as fast
b) it is 1/2 as fast
c) it is 2 times as fast
d) it is 4 times as fast

  v₂ = 2 v₁   blood velocity in the built zone is twice the speed of the normal zone,   so the correct response is c

Explanation:

For that problem we must use the fluid continuity equation

          A₁ v₁ = A₂ v₂

Where point 1 is in the normal artery and point 2 in the contraction

         v₂ = v₁  A₁ / A₂

In the exercise indicates

          A₂ = ½ A₁

          v₂ = 2 v₁

The blood velocity in the built zone is twice the speed of the normal zone, so the correct response is c