GEOG 3P83 Midterm: GEOG 3P83 Midterm Exam Notes
This geometry task may be helpful for devising amathematicalprocedure for the next lab.
A right triangle has legs ofknown lengths 2L and h. Find thelength of the line segment x whichis parallel to side h. Explainyour reasoning. Image in weblinkbelow:
POSTSCRIPT: EFFECTS OFASSUMPTIONS
The marbled murrelet is asmall bird that lives in the PacificNorthwest where old-growthforests are close to the sea. It nests inthe forests and feedsoffshore. It is now highly endangeredthroughout its range, whichextends from Northern California toAlaska.
These birds are extremelyvulnerable to loss of their habitat,because they nest exclusivelyin the same old-growth coniferoustrees that are prime targets forlogging. Considerable efforts havebeen made to protect the speciesby restricting timber operations inthe areas in which they areknown to nest. Scientists predicted thatthe population should growback. However until recently naturalistswere puzzledand
dismayed because thepopulation of marbled murrelets did notseem to be recovering oreven stabilizing.
A recent study suggests thereason why this testing experimentin conservation did not confirmthe prediction. The scientistsoverlooked an important assumption:murrelets can also be threatenedby man's activity at sea.Overfishing has severely reduced thepopulation of small,energy-rich fish that murrelets rely upon formost of theircalories.
Climate change of uncertainorigin may have also disrupted thefood chain, and El Nino currentsmay have changed the distributionof the phytoplankton that formsthe base of all marine life.
Further efforts to preservethe marbled murrelet must be basedon accurate assumptions aboutthe origin of their difficulties.
Could naturalists have betterconsidered their originalassumptions years ago? What would yousay?
) 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?
-) 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.)
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?
20. Which of the following processes will NOT cause a gas cloudtocollapse?
Aionization from youngstars
Dthe expansion of theUniverse
22. White dwarf stars are supported from collapse by
Anuclear fusionreactions in a shell around the core.
Cnuclear fusion reactionsin their cores.
Dcentrifugal force due torapid rotation.
23. The "star" that is seen at the center of a planetarynebulais
Aa planet in theprocess of formation.
Ba small, hot, and verydense, white dwarf star.
Cthe accretion disk arounda black hole.
Dcomposed almost entirelyof neutrons, and is spinning rapidly.
24. A white dwarf star, the surviving core of a low-massstartowards the end of its life, can be found ontheHertzsprung-Russell diagram
Aat the bottom end ofthe main sequence, along which it has evolvedthroughout itslife.
Babove and to the right ofthe main sequence, since it evolved thereafter itshydrogen-burning phase.
Cbelow and to the left ofthe main sequence.
Dat the upper left end ofthe main sequence, since its surfacetemperature is extremelyhigh.
25. The mechanism which gives rise to the phenomenon of thenovais
Amaterial fallinginto a black hole and being condensed to the pointwhere athermonuclear explosion is produced.
Bthe impact and subsequentexplosion of a large comet nucleus upon astar's surface.
Cthe completedisintegration of a massive star because ofthermonuclear runawayin the star's interior.
Dmatter from a companionstar falling onto a white dwarf in a closebinary system,eventually causing a nuclear explosion on thedwarf'ssurface.