According to Bernoulli's principle,
$P + \frac{1}{2} d v^2 + dgh = constant$
where, P is pressure, d is density of water, v is velocity and h is height.
Assuming that height of a plastic pipe is kept constant, we get => $P + \frac{1}{2}dv^2 = \text{constant}$.
Now, if we narrow the outlet of the pipe by obstructing the flow of water, both, the speed of the water coming out as well as its pressure increases. For Bernoulli's principle to be true, one has to decrease for the other to increase…
So, how can Bernoulli's principle be correct after this counterexample?
Best Answer
No,the velocity increases but the pressure decreases. This pressure that you are refering to,is the dynamic pressure,it is the pressure that drives the fluid.That keeps the momentum going. The fluid entering the narrower piece of pipe means that fluid tends to push back the fluid that tries to enter after it.That compresses the micro movements of the tiny particles,thus lowering that dynamic pressure(the micro movements are the causes for pushing the fluid).