# Fluids in Motion

#### jgalt42

7+ Year Member
Hey guys,

In my EK book it says uniform translational fluid motion does not contribute to fluid pressure, but when it talked about Bernoulli's equation it said that as velocity increased, pressure decreases. Is this a mistake or are these two different pressures?

#### G1SG2

10+ Year Member
5+ Year Member
Hey guys,

In my EK book it says uniform translational fluid motion does not contribute to fluid pressure, but when it talked about Bernoulli's equation it said that as velocity increased, pressure decreases. Is this a mistake or are these two different pressures?
Yes, that is essentially what Bernoulli's equation states. Think of it as conservation of energy. Pressure decreases as velocity increases (sort of like how when you drop a ball from a certain height, gravitational potential energy is exchanged for kinetic energy, and vice versa when you throw the ball up from the ground).

#### inaccensa

10+ Year Member
7+ Year Member
Yes, that is essentially what Bernoulli's equation states. Think of it as conservation of energy. Pressure decreases as velocity increases (sort of like how when you drop a ball from a certain height, gravitational potential energy is exchanged for kinetic energy, and vice versa when you throw the ball up from the ground).

I'm getting confused with these fluids.

In a non-ideal fluid such as blood flowing through the vascular system, based on dP= QR & Q=Av and dp= AvR. Someone else explained it this way. So
when the RESISTANCE increases, PRESSURE, VELOCITY increases.
when the AREA increases, PRESSURE, VELOCITY DECREASES.

In ideal fluids, pressure and velocity are proportional

P= F/A when area increases, pressure decreases & velocity decreases?
similarly with increases in resistance, velocity decreases right, since resistance is loss of energy. How does this whole thing come about.

OP
J

#### jgalt42

7+ Year Member
Why does an increase in the velocity of a fluid decrease the temp?