physics
posted by sarah .
The volume flow rate in an artery supplying the brain is 3.10 106 m3/s.
(a) If the radius of the artery is 4.50 103 m, determine the average blood speed.
1 m/s
(b) Find the average blood speed at a constriction in the artery if the constriction reduces the radius by a factor of 4. Assume that the volume flow rate is the same as that in part (a).

Velocity = Q/A, where Q is the volume flow rate.
If r is reduced by a factor of 4, area is reduced by a factor of 16, and velocity increases by that factor