The platelets are drifting with the blood flowing in a streamline flow through a horizontal artery as shown below :

Artery is contracted in region II. Choose the correct statement.

Options

A. As the platelets enter a constriction , the platelets gets squeezed closer together in the narrow region and hence the fluid pressure must rise there.
B. As the platelets enter a constriction , pressure is lower there.
C. The artery's cross section area is smaller in the constriction and thus the pressure must be larger there because pressure equals the force divided by area
D. Pressure is same in all the parts of the artery

Answer

B

Explanation

Using equation of continuity
`A_1V_1-A-2V_2`
where `A_1` & `A_2` are cross-section area of region I & region-II.
as `A_2ltA_2`
`rArrV_2gtV_1`
Using Bernouilli’s equation
`P+1/2pv^2`= constant
as `V_2gtV_1`
`P_2ltP_1`
therefore pressure will be lower at constriction.