Question

Picture water flow of four straws, short and fat, short and thin, long and fat, and long and thin.

Think about how water would flow through two configurations of these same four straws:

One version where the four straws are taped end-to-end to make one long straw

The other version where all four straws are taped together side by side, so you would suck water through all four at the same time

Which of these two configurations produces the lowest current? Which produces the highest? Why?

Answer 1

Assumption, water to be incompressible.

How we suck water through the straw, we reduce the pressure inside the straw, such that it is lower than atmospheric pressure. Hence due to it creates a slight vacuum condition in the straw and hence water is sucked up.

Assume that in bothe the condition you apply the same pressure (i.e sucking strength is same) the pressure difference is same in both the configuration.

In configuration 1, it will take longer for the water to reach your mouth than in 2nd configuration. But once the situation stablizes and water current becomes steady, the flow velocity will depend only on the pressure difference and not on the length of the straw.

However, the water current is (amout of water flowing /unit time). In configuratuon 1 the flow area is much less than that of configuration 2. Configuration 2 provides more area to flow, Hence the water current is more in configuration 2 than in 1.

( you can understand this with the anology of electric current, 1st config is series cinnection of resistors, and 2nd config is parallel config of resistors.)