Question #8ae4b

1 Answer
Mar 25, 2017

Drawn

Given that an ideal fluid flows in the tube as shown figure.

The pressure of the fluid at the bottom #(P_2)# is equal to the pressure of the fluid at the top #(P_1)# i.e. #(P_1=P_2)# )

The difference in height of the top and bottom #h_1-h_2=3m#

The velocity of the fluid at the top #v_1=2m"/"s#

The velocity of the fluid at the bottom #v_2="unknown"#

The area of cross-section of the pipe at the top #A_1#

The area of cross-section of the pipe at the bottom #A_2#

We are to find out the ratio of #A_1:A_2#

Now applying Bernoulli principle

#"Energy per unit volume at the top"= "Energy per unit volume at the bottom"#

we have the following equation

#P_1+1/2rhov_1^2+rhogh_1=P_2+1/2rhov_2^2+rhogh_2#

where

#rho= "density of the fluid"#

#and g = "acceleration due to pop gravity"=10m"/"s^2 #

Inserting given values in the above equation we get

#cancelP_2+1/2cancelrho2^2+cancelrho10h_1=cancelP_2+1/2cancelrhov_2^2+cancelrho10h_2#

#=>2+10h_1=1/2v_2^2+10h_2#

#=>2+10h_1-10h_2=1/2v_2^2#

#=>2+10(h_1-h_2)=1/2v_2^2#

#=>2+10xx3=1/2v_2^2#

#=>v_2^2=64#

#=>v_2=sqrt64=8m"/"s#

Now applying principle of continuity of flow of ideal fluid we can write

#A_1/A_2=v_2/v_1=(8m"/"s)/(2m"/"s)=4/1# which is option (2)