Water pressure in two pipes.

Question

Which one of the below presents a higher pressure at the bottom?

a) 16 ft tall pipe, 40cm diameter.

b) 197 inches tall pipe, 20cm diameter, changing to 1cm diameter at the last 1 meter at the bottom.

consider both pipes are side by side, bottom at the same level, pipes full of water, same temperature.

Answer 1

16*12=192,

so "B" is higher.

diameter is irrelevant to pressure.

well static pressure that is.

if the fluid's flowing, then the problem becomes a bit more complicated.

Answer 2

According to Torricelli's theorem,            

neglecting diameters,

h1=16ft=4.8768m

h2=197in.=5.0038m                          

velocity at bottom of pipe a=V1=sqr root(2*g*h1)=9.86 m/s

velocity at bottom of pipe b=V2=sqr root(2*g*h2)=10.003 m/s

By Bernoulli's effect, in a closed pipe, where velocity is more, pressure will be less.

Therefore, because V2>V1, (a) will present a higher pressure at the bottom.

Answer 3

Pressure is force/unit area. The

diameter of the pipe is not important.

The taller pipe is the answer:

16 foot pipe = 16*12 = 192 inches

other pipe=197 inches:correct answer