Enable contrast version

# Tutor profile: Carlos O.

Inactive
Carlos O.
Tutor for Earth Sciences, Biology and English
Tutor Satisfaction Guarantee

## Questions

### Subject:Environmental Science

TutorMe
Question:

What is the difference between the center of mass of rainfall and the center of mass of runoff?

Inactive
Carlos O.

The center of mass of rainfall is the point at which half of the total rainfall has fallen over a period of time. That means that you need to have data regarding how long the rain has fallen over the period of time that you wish to investigate, and you also need to measure how much rain fell per unit of time. Once you have that information, you can calculate when 50% of the rain had already fallen. This is the center of mass of rainfall. The center of mass of runoff is very similar. It is the point at which half of the total runoff has already happened. Again, you need to have information over the period of time you wish to investigate about how much runoff happened per unit of time and then you can calculate when, along that time period, 50% of the total runoff had already happened.

### Subject:Earth Science

TutorMe
Question:

Why is it that permeability and porosity aren't always directly related?

Inactive
Carlos O.

Porosity is a description of the physical condition of a material: how much of this material is just empty space, how many holes does it have? Primary porosity is a reflection of the amount of pores within the material itself. Secondary porosity is a reflection of the amount of other spaces caused by external factors, like tunneling animals, or tree roots. Permeability, on the other hand, is a description of how well a fluid can travel through the pores of the material. Permeability will depend on the kind of fluid we study. If it is water, for example, then permeability will reflect the system's hydraulic viscosity: how well water can move through the pores in the system. Materials with low permeability typically promote erosion and have higher runoff rates. In short, permeability depends on porosity and it integrates other factors too, like viscosity of the fluid. As a couple of examples: sandstone is somewhat porous and has moderate permeability, which encourages flow of fluid throughout its entire structure. However, granite, for example, has extremely low permeability and extremely low porosity, which encourages higher runoff and surface erosion.

### Subject:Environmental Engineering

TutorMe
Question:

What is a simple explanation of Darcy's Law?

Inactive
Carlos O.

Darcy’s law gives information on the flow (Qout ) of a fluid through porous material depending on the following factors: hydraulic conductivity, the cross-sectional area of the soil column, and the hydraulic gradient. Hydraulic conductivity, K, is a measure of how well water can travel across the material. The cross-sectional area of the column, Ac, indicates how wide the tunnel through which the fluid is moving is (the bigger the cross-sectional area, the greater the flow). The hydraulic gradient is a measure of the difference in height , Δh , over the difference in length, Δl, of the soil column. The bigger the difference in height, for example, the more flow you will get because of gravity. The bigger the difference in length, the longer it will take for the fluid to traverse the material. Qout = KAcs(Δh/Δl)

## Contact tutor

Send a message explaining your
needs and Carlos will reply soon.
Contact Carlos

Start Lesson

## FAQs

What is a lesson?
A lesson is virtual lesson space on our platform where you and a tutor can communicate. You'll have the option to communicate using video/audio as well as text chat. You can also upload documents, edit papers in real time and use our cutting-edge virtual whiteboard.
How do I begin a lesson?
If the tutor is currently online, you can click the "Start Lesson" button above. If they are offline, you can always send them a message to schedule a lesson.
Who are TutorMe tutors?
Many of our tutors are current college students or recent graduates of top-tier universities like MIT, Harvard and USC. TutorMe has thousands of top-quality tutors available to work with you.
BEST IN CLASS SINCE 2015
TutorMe homepage