Question

For which case will the viscosity increase, keeping all other factors constant?

	a.	The force applied to the surface of the fluid increases
	b.	The height of the fluid column decreases
	c.	The velocity of the fluid increases
	d.	The cross-sectional area increases

If the flow rate and time are known, what else about the fluid can be found?

	a.	Pressure
	b.	Cross-section area
	c.	Volume
	d.	Velocity

For which case will the flow rate decrease for Poiseuille flow?

	a.	The radius of the tube increases
	b.	The viscosity decreases
	c.	The tube length decreases
	d.	The pressure difference decreases

Some questions I'm struggling with! Help is appreciated!

Answer 1

For which case will the viscosity increase, keeping all other factors constant?

let's write the viscocity equation:

$\eta =\frac{F/A}{dv_{x}/dz}$

where F is the applied force, A is the area of the cross section and $dv_{x}/dz$. is the velocity gradient.

Observing the above equation, the viscosity increases if the force applied to the fluid surface increases (the correct option is the part a).

If the flow rate and time are known, what else about the fluid can be found?

Knowing the flow rate and time, you can determine the speed of the fluid (option d).

For which case will the flow rate decrease for Poiseuille flow?

The equation for the poiseuille flow is as follows:

$volume flow=\frac{(pressure difference)(radio)^{4}}{8/\pi (viscosity)(length)}$

observing the previous equation, the flow decreases as the pressure difference decreases (option d).