Calculate pressure using Bernoulli's equation

In summary, the conversation discusses the task of showing that human lungs would be unable to drink a milkshake through a vertical straw. The given information includes the density of the milkshake, the dimensions of the glass and straw, and the desired pressure difference of 3000Pa. The conversation also mentions the need to calculate the pressure difference and the velocity of the liquid, and suggests using the difference between atmospheric pressure and air pressure in the lungs. The conversation ends with a suggestion to consider the density of air and the height difference of the straw in relation to the capacity of the human lungs.
  • #1
09matthew
7
0

Homework Statement


You have been given a milkshake (ρ = 1200kg/m^3). The glass is 200mm tall a straw 8mm diameter and 300mm long. Show that human lungs would be unable to drink the milkshake through a vertical straw. (answer should be around 3000Pa)

I have no idea what to do as I don't know how to find the speed and also not sure if P1 is atmospheric pressure or not. Any help would be greatly appreciated!

Thank you!

Homework Equations

The Attempt at a Solution

 
Physics news on Phys.org
  • #2
09matthew said:
You have been given a milkshake (ρ = 1200kg/m^3). The glass is 200mm tall a straw 8mm diameter and 300mm long.[/QUOTE
i think one should calculate the pressure difference required for the liquid to rise to the upper point of the straw and the velocity of the liquid may be sufficient only to pour out in the mouth- one can take a unit volume for estimation of the required pull from the lungs.
 
  • #3
09matthew said:
Show that human lungs would be unable to drink the milkshake through a vertical straw.

suppose a person sucks out air from the straw the liquid can rush to the top by difference of pressure - the atmospheric pressure and the air pressure in side the mouth which is air pressure in the lungs- try to calculate it and see how it comes out!
 
  • #4
Sorry, I'm still not so sure where to start... how would i get the pressure difference? and also, is z1 = 200mm (size of the cup) and z2 = 300mm (size of the straw)?
 
  • #5
09matthew said:
and also, is z1 = 200mm (size of the cup) and z2 = 300mm (size of the straw)?

one can dip the straw ,so that the height difference is only( z2 -z1) -the human lung can take average about 6 litres of air.
 

What is Bernoulli's equation?

Bernoulli's equation is a mathematical equation that relates the pressure, velocity, and height of a fluid in a steady flow. It states that the total energy of a fluid remains constant throughout the flow.

How is Bernoulli's equation used to calculate pressure?

Bernoulli's equation can be rearranged to solve for pressure by subtracting the kinetic energy and potential energy terms from the total energy term. This results in the equation P1 + 1/2ρv1^2 + ρgh1 = P2 + 1/2ρv2^2 + ρgh2, where P is pressure, ρ is density, v is velocity, and h is height.

What are the units of each term in Bernoulli's equation?

The units of pressure are typically measured in pascals (Pa), the units of velocity are meters per second (m/s), and the units of height are meters (m). Density is typically measured in kilograms per cubic meter (kg/m^3). It is important to ensure that all units are consistent when using Bernoulli's equation to calculate pressure.

Can Bernoulli's equation be used to calculate pressure in any fluid?

Bernoulli's equation can be used to calculate pressure in any fluid that is in a steady flow. However, it is important to note that it assumes the fluid is incompressible, non-viscous, and irrotational. These assumptions may not hold true for all fluids, so caution should be taken when using the equation.

How can Bernoulli's equation be applied in real-world situations?

Bernoulli's equation has many practical applications, such as calculating the pressure drop in a pipe system, determining the lift force on an airplane wing, and understanding the flow of blood in the human body. It is also commonly used in the design and analysis of pumps, turbines, and other fluid systems.

Similar threads

  • Engineering and Comp Sci Homework Help
Replies
8
Views
8K
  • Thermodynamics
Replies
11
Views
254
  • Introductory Physics Homework Help
Replies
2
Views
1K
  • Mechanical Engineering
Replies
31
Views
2K
  • Engineering and Comp Sci Homework Help
Replies
30
Views
4K
Replies
48
Views
4K
  • Engineering and Comp Sci Homework Help
Replies
6
Views
2K
  • Introductory Physics Homework Help
Replies
5
Views
3K
  • Engineering and Comp Sci Homework Help
Replies
10
Views
3K
  • Engineering and Comp Sci Homework Help
Replies
5
Views
2K
Back
Top