Who doesn't love a good espresso? But as I'm sure every great barista knows, the real key is all about permeability...As every great barista also knows, the ideal espresso shot (double, of course) is 60 ml, extracted at a brewing temperature of 94 degree C and a pressure of 9 bars, and takes 26 seconds to "pull". The standard diameter of the brewhead (and therefore of the coffee "puck" through which the water flows) is 58 mm. The "puck" is typically 7/8" thick. (A) What are the hydraulic conductivity and permeability of the ideal espresso puck? Be mindful that fluid properties (density and viscosity) are dependent on temperature, so you'll need to do some digging for the right values. (B) In the case of the overzealous home barista, a common mistake is to grind the coffee too coarse or too fine. Suppose all of the above parameters are the same, except that the result is a measly 25 ml espresso shot that takes 57 seconds to produce. What's the permeability of that puck 13 pts, and what should be changed to fix the problem?

carbon is found in all living things. carbon atoms move constantly through

living organisms, the oceans, the atmosphere, and the earth’s crust in what is

known as the carbon cycle. the directions taken by carbon atoms through this

cycle are very complicated and can take millions of years to make a full circle.

all animals, from humans to the dinosaurs are part of the carbon cycle. when

animals eat food, they get carbon in the form of carbohydrates and proteins.

in animals, oxygen combines with food in the cells to produce energy for daily

activity and then gives off carbon. the carbon combines with oxygen to form

carbon dioxide (co2) and is released back into the atmosphere as a waste

product when animals breathe and exhale.

from 145-65 million years ago, earth was much

hotter than today and covered with dense,

tropical swamp forests. the trees and other

plants were immense and

provided an endless supply of

food for the giant animals that

roamed the land. somewhere in

the air above one of these

forests, a lone carbon atom has joined

up with two oxygen atoms to form a molecule of co2.

the co2 molecule was sucked into the tiny holes (stomata) on the leaf of a

fern plant and joined with sunlight, chlorophyll and water to make food and

energy in the plant’s cells through photosynthesis. the oxygen (o2) from the

co2 molecule was sent back into the atmosphere; the carbon atom (c) was

detached and used to make a molecule of sugar.

if that carbon atom had been eaten instead, a totally

different situation would have developed. let’s say

that a giant plant-eating dinosaur (herbivore) ate the

fern for breakfast, and swallowed the carbon in the

fern in the form of carbohydrates and proteins. in

the process of respiration, oxygen combined with

the carbohydrates and proteins in the dinosaur’s cells

to provide energy for its daily activity.  

answer: 31, 5556. 952 seconds