IB Physics – Grade 11 – Model Answers for Exam Prep

Exam date: 11 March 2013

Topics to prepare for :

• Unit 2. 7:  Mechanics: Work, Power, Energy       Chapter 2.7C
• Unit 2. 8:  Circular motion                                Chapter 2.8C
• Unit 2. 9:  The law of Gravitation                       Chapter 2.9C
• Unit 2.10:  Projectile motion                              Chapter 2.10C
• Unit 3.  1:  Thermal concept                              Chapter 3.1C
• Unit 3.  2:  Thermal properties                           Chapter 3.2C
• Unit 4.  1:   Simple Harmonic Motion                  Chapter 4.1C
• Unit 4.  2:  Traveling wave characteristics           Chapter 4.2C
• Unit 4.  3:  Wave phenomena I                           Chapter 4.3C
• Unit 4.  4:  Wave phenomena II                          Chapter 4.4C
• Unit 4.  6:  Standing waves                                Chapter 4.6C

The Drake Equation

Hey, check out this cool equation …

The Drake equation states that:

where:

N = the number of civilizations in our galaxy with which communication might be possible (i.e. which are on our current past light cone);

and

R^* = the average rate of star formation per year in our galaxy

f_p = the fraction of those stars that have planets

n_e = the average number of planets that can potentially support life per star that has planets

f_ℓ = the fraction of the above that actually go on to develop life at some point

f_i = the fraction of the above that actually go on to develop intelligent life

f_c = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space

L = the length of time for which such civilizations release detectable signals into space

Physics Grade 11 Exam – 11 March 2013

The next Exam for Physics IB DP SL (Grade 11) will on 11 March 2013

Topicts prepare for are:

• Unit 2. 7:  Mechanics: Work, Power, Energy
• Unit 2. 8:  Circular motion
• Unit 2. 9:  The law of Gravitation
• Unit 2.10:  Projectile motion
• Unit 3.  1:  Thermal concept
• Unit 3.  2:  Thermal properties
• Unit 4.  1:   Simple Harmonic Motion
• Unit 4.  2:  Traveling wave characteristics
• Unit 4.  3:  Wave phenomena I
• Unit 4.  4:  Wave phenomena II
• Unit 4.  6:  Standing waves

A weighted approach with more weight given to Chapter 4 topics

STARDUST

The STARDUST Mission

( from http://stardust.jpl.nasa.gov/mission/index.html )

Mission Overview Stardust is the first U.S. space mission  which is  …. dedicated solely to the exploration of a comet, and                     the first robotic mission designed to return extraterrestrial material from outside the orbit of the Moon. The Stardust spacecraft was launched on February 7, 1999, from Cape Canaveral Air Station, Florida, aboard a Delta II rocket. The primary goal of Stardust is to collect dust and carbon-based samples during its closest encounter with Comet Wild 2 – pronounced “Vilt 2” after the name of its Swiss discoverer – is a rendezvous scheduled to take place in January 2004, after nearly four years of space travel. Additionally, the Stardust spacecraft will bring back samples of interstellar dust, including recently discovered dust streaming into our Solar System from the direction of Sagittarius. These materials are believed to consist of ancient pre-solar interstellar grains and nebular that include remnants from the formation of the Solar System. Analysis of such fascinating celestial specks is expected to yield important insights into the evolution of the Sun its planets and possibly even the origin of life itself. In order to meet up with comet Wild 2, the spacecraft will make three loops around the Sun. On the second loop, its trajectory will intersect the comet. During the meeting, Stardust will perform a variety of tasks including reporting counts of comet particles encountered by the spacecraft with the Dust Flux Monitor, and real-time analyses of the compositions of these particles and volatiles taken by the Comet and Interstellar Dust Analyzer (CIDA). Using a substance called aerogel, Stardust will capture these samples and store them for safe keep on its long journey back to Earth. This silica-based, material has been inserted within the Aerogel Collector Grid, which is similar to a large tennis racket. Not until January 2006, will Stardust and its precise cargo return by parachuting a reentry capsule weighing approximately 125 pounds to the Earth’s surface. Stardust is the fourth NASA Discovery mission to be chosen and follows on the heels of Mars Pathfinder, the Near Earth Asteroid Rendezvous (NEAR) mission, and the Lunar Prospector mission. The Discovery Program, is an ongoing program that is intended to offer the scientific community opportunities to accomplish frequent, high quality scientificinvestigations using innovative and efficient management approaches. It seeks to keep performance high and expenses low by using new technologies and strict cost caps. Stardust is managed for NASA’s Space Science Division by the Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology (Caltech). Stardust is a collaborative partnership between the University of Washington, Lockheed Martin Astronautics and JPL/Caltech. The principal investigator, Dr. Donald Brownlee of the University of Washington leads a global team of scientists worldwide.

STARDUST

The following link/page is a MUST READ:

Stardust – NASA

 

How Comets Work

by Craig Freudenrich, Ph.D.

(from: http://science.howstuffworks.com/dictionary/astronomy-terms/comet3.htm)

Nucleus of Halley’s comet taken from the Giotto mission.

(This is a false color image of the nucleus of Halley’s comet taken from the Giotto mission. Note the jets of evaporating gas coming from the nucleus on the left side.)

Courtesy of NASA/NSSDC Planetary Image Archives

Parts of a Comet

As a comet approaches the sun, it warms up. During this warming, you can observe several distinct parts:

• nucleus
• coma
• hydrogen envelope
• dust tail
• ion tail

The nucleus is the main, solid part of the comet. The nucleus is usually 1 to 10 kilometers in diameter, but can be as big as 100 kilometers. It can be composed of rock.

The coma is a halo of evaporated gas (water vapor, ammonia, carbon dioxide) and dust that surrounds the nucleus. The coma is made as the comet warms up and is often 1,000 times larger than the nucleus. It can even become as big as Jupiter or Saturn (100,000 kilometers). The coma and nucleus together form the head of the comet.

Surrounding the coma is an invisible layer of hydrogen called the hydrogen envelope; the hydrogen may come from water molecules. It usually has an irregular shape because it is distorted by the solar wind. The hydrogen envelope gets bigger as the comet approaches the sun.

The comet’s dust tail always faces away from the sun. The tail is made of small (one micron) dust particles that have evaporated from the nucleus and are pushed away from the comet by the pressure of sunlight. The dust tail is the easiest part of the comet to see because it reflects sunlight and because it is long, several million kilometers (several degrees of the sky). The dust tail is often curved because the comet is moving in its orbit at the same speed that the dust is moving away, much as water curves away from the nozzle of a moving hose.

Comet Halley as it appeared in several images from the 1910 apparition. The comet’s tail gets bigger as it gets closer to the sun and then decreases as it moves away from the sun.

Photo courtesy NASA/JPL

Comets often have a second tail called an ion tail (also called the plasma or gas tail). The ion tail is made of electrically charged gas molecules (carbon dioxide, nitrogen, water) that are pushed away from the nucleus by the solar wind. Sometimes, the gas tail disappears and later reappears when the comet crosses a boundary where direction of the sun’s magnetic field is reversed.

Comet dust seeding life to Jupiter moons?

by Staff Writers Boulder, Colo. (UPI) Feb 15, 2013

(from:  http://www.spacedaily.com/reports/Comet_dust_seeding_life_to_Jupiter_moons_999.html)

Comet dust may have seeded Jupiter’s moons, including Europa and its liquid ocean beneath an icy crust, with the raw ingredients for life, U.S. researchers say.

Asteroids and comets rich in the carbon-containing compounds that are key to life on Earth have been captured by Jupiter’s gravity, becoming orbiting moons that frequently collided as they settled into new orbits billions of years ago and created a fine dust of those compounds, they say.

The question is, where has all that dust gone?

Computer models suggest Jupiter should have captured about 70 million gigatons of rocky material but less than half that amount remains as irregular moons orbiting the planet.

William Bottke of the Southwest Research Institute in Boulder, Colo., said the ground-up material would have fallen toward Jupiter, dragged by gravity and blown by the solar wind and almost half of it would have hit Jupiter’s largest moons, including Callisto, Ganymede and Europa.

Images from NASA’s Galileo spacecraft have shown dark material on Ganymede and Callisto.

“Callisto literally looks like it’s buried in dark debris,” Bottke told NewScientist.com, noting the surface of Ganymede looks similar.

In comparison, Europa’s surface appears relatively clean but cracks in the moon’s icy crust suggest material is being cycled from the surface to deeper inside.

Carbon-rich debris settling on Europa may have been incorporated into the ice and made it into the ocean, Bottke said.

“Would it be important in Europa’s ocean? It’s hard to say,” he said. “But it is kind of interesting to think about.”