This problem will be compared to the problem of natural convection from the ground. a team of soil scientists are interested in finding out how much grasses contribute to heat transfer from the earth surface to the ambient air, thereby cooling down the surface temperature. they model that the grass blades act as fins. the ground temperature is 33 c, while the air above is 22 c. we estimate that the heat transfer coefficient h-1.0 w/m2-c (not the value in the other problem). the ground is horizontal and flat, of size 20 m by 20 m surrounded by a fence. the grass is 8.0 cm long, and we will apprpximate that each blade has a rectangular cross section 0.1 mm 1.0 mm, of uniform cross section. an approximate value of the conductivity k is 40% of water, or 0.24 w/m-c. there are about 50 blades of grass per cm2- 500.000/m2- 200 million on the whole plot of ground. what is the heat loss from the ground due to the grass acting as fins? .
a)-74 w b)-15,000 w c)-2,200 w d)-0.0322 e)-610w

Fill in the blanks with the numbers is a measure of the resistance to flow. a high liquid has a high resistance to flow and flows slowly. the ancients thought everything in the world was made of 4 we now know that there are 94 naturally occurring and scientists have created another 24 i am certain they will create even more. honey flows slowly because it has a high to flowing. a can be separated by physical means because it contains more than one pure substance and 2 pure substances are not chemically bonded to each other. a cannot be separated by physical means. all matter is made up of all elements are with the same number of protons. if it is just a single or many bonded together, if all of them have the same number of protons, it is an element. in a piece of pure iron metal, all the are joined together, that piece of iron metal is called elemental iron. a single of iron is called elemental iron. a mixture has differences from place to place. we might need a microscope to see them or they might be obvious to the unaided eye. there are surfaces separating it into different phases. a mixture is the same everywhere. it is uniform. there are no surfaces separating it into different phases. if different kinds of atoms (different elements) are bonded together by their electrons, it is called a there are physical means of to isolate the different pure substances in a mixture and there are chemical means of to isolate the different elements in a compound. 1. element 2. compound 3. mixture 4. heterogeneous 5. homogeneous 6. pure substance 7. atoms 8. separation 9. viscosity 10. resistance