AST251H1 Lecture : AST251 FEBRUARY 27.docx

38 views8 pages

salmondog80

4 Mar 2012

School

UTSG

Department

Astronomy & Astrophysics

Course

AST251H1

Professor

Susan Pfieffer

For unlimited access to Class Notes, a Class+ subscription is required.

Document Summary

The origins of life most likely occurred 4. 5 and 3. 5, isotope ratios 4 billion and fossils 3. 5 gyr. The cambrian explosion refers to 545 million years ago: origins, oxygen and eukarya, cambrian explosion, k-t event, humans. Essential elements already on earth and water brough to us. Replication with heredity and rna and dna. Little oxygen was dominated by h compounds red or orange and hot bc earth was still hot. Water of earth only makes up . 1 percent of the mass. 2 percent water all land convered by water. 2 crust ocean which is heavy sinlks and lighter continental crust. 1920s gaqs mixture of earths atmosphere, and added sparks to it produced different types of amino acids, important step in demonstrating complex molecules can form spontaneously. Pungent ponds organic soup, vuln to uv and impacts. Atmosphere different from what they assumed to.

Related Questions

) Ion Rocket Engine. A special type of rocket engine useselectricity for propulsion: the ion engine. A soft metal, such ascesium, is vaporized and then electrified (ionized) with highvoltage. These cesium ions are the accelerated by strong electricfields to produce a current of atoms at high velocity. Outside theengine, the ions are then recombined with electrons to restoreelectrical neutrality.

A particular ion engine has an exhaust velocity of 20,000 m/sec.The mass flow (dm/dt) is just 1 milligram per second.

a) What is the thrust produced by this engine?

b) The engine propels a 200 kg spacecraft. What velocity change(delta-v) is achievable by running the engine continuously for onesolid year? (For simplicity, assume a constant mass for the system.One year = 31.56 million seconds.)
---------------------------
) Potential Energy. How much work is required to lift one metricton (1000 kg) of water to an altitude of 1000 meters? (The Sun isdoing this all this time to the Earthâs weather.)
--------------------------------

q) Kinetic Energy 1. A car has a mass of 1200 kg. How much kineticenergy does it have when traveling at a speed of 30 m/sec?

-----------------------
Kinetic Energy 2. The Space Shuttle orbits the Earth at a speed ofsome 7750 meters per second (which is about 260 times that of atypical highway driving speed). With a typical payload, the Shuttlehas a mass of 120,000 kg.

a) What is the kinetic energy of the Shuttle in orbit?
b) The Shuttle reaches orbit in some 500 seconds. At what rate ofwork (power) did the rocket engines perform on the Shuttle to placethe craft and its payload into orbit? Compare this to the maximumpower output of a typical nuclear electric generatingstation.
-----------------------

Solar Power. In space, outside the atmosphere, some 1360 Watts ofradiant power pass through every square meter (at normalincidence).

a) What total amount of power does the Earth intercept from theSun? (The projected area of the Earth is ?RE2, where RE is theradius of the Earth, 6.38 million meters.)

b) Compare this figure to the total amount of power produced by allof human civilization, currently some 40 trillion (1012) Watts.What conclusions about solar power can you draw from thiscomparison?

q

-) Angular Momentum. Assuming a uniform distribution of mass insidethe Earth, calculate:

a) the Earthâs moment of inertia, I;
b) its angular momentum, L = omega(omega=2pi/T) the angularmomentum of the Moon in its orbit around the Earth (L = mvr).Compare these two values. (The sidereal period of the Moon is 27.3days; its mass is 1/81 of that of the Earth; its average orbitalradius is 383,000 km.)

------------------------------------

Q0 Water Pressure. Calculate the value of the water pressure at theChallenger Deep, the deepest known place on the surface of theEarth. The currently accepted depth of the water there is 10,911meters. (This is deep enough to cover Mount Everest, and still havemore than one mile of water above the peak. On January 23, 1960,Swiss explorer Jacques Piccard and US Navy Lieutenant Don Walshbecame the first, and so far, the only people ever to visit thisremote place, descending in the Italian-built bathyscaphTrieste.)

q-8
Mass of Earthâs Atmosphere. The pressure of the Earthâs atmosphereat sea level is 101,300 Pascals (Newtons per square meter.) Thismeans that every square meter of Earthâs surface supports a weightof 101,300 Newtons. From this, determine the mass of Earthâsatmosphere. What fraction of the Earthâs total mass is this?

AST251H1 Lecture : AST251 FEBRUARY 27.docx

Document Summary

Get access

Related Questions