Velocity in Hoses: Why is it Low and What Does it Mean?

[werson tan]

Homework Statement

in the second photo , why the velocity inside the hose is relatively low ? If it is low , the water wouldn't be able to move out of the hose , am I right ?

Homework Equations

The Attempt at a Solution

 

[BvU]

Did you read the template headers ?

What the writer means is that the exit opening of the hose is considerably smaller than the diameter.

 

[werson tan]

Did you read the template headers ?

What the writer means is that the exit opening of the hose is considerably smaller than the diameter.

how it relate to the V1 ?

 

[BvU]

It doesn't. The volume flow is not playing a role in this exercise, where the upper limit of the achievable height is calculated.

 

[werson tan]

It doesn't. The volume flow is not playing a role in this exercise, where the upper limit of the achievable height is calculated.

you mean when the diameter in the hose is larger , the velocity of water in the hose is much smller ( almost = 0 ) compared to the velocity of water at the escaping hole ?

 

[BvU]

Bernoulli equation is an energy balance. Here the pressure energy (difference) is converted into gravitational potential energy. The upper limit for height follows if the kinetic energy in the hose can be ignored.

And indeed, at the outflow opening there is mainly kinetic energy.

 

[werson tan]

Bernoulli equation is an energy balance. Here the pressure energy (difference) is converted into gravitational potential energy. The upper limit for height follows if the kinetic energy in the hose can be ignored.

And indeed, at the outflow opening there is mainly kinetic energy.

ok , so is my statement in post #5 correct ?

 

[BvU]

I would say: yes it is. You can conclude v² in the hose is ignored wrt v² at the outflow opening.

I tried to talk around that a bit, since there is a small issue of what exactly happens at the outflow opening: a high v means a low p