Transcript Notes for Class 8, March 3

Schedule:
• Review (Q & A) up to 6 PM
• Midterm (about one hour)
• Return graded work and
turning work in
• Class (about 1¼ hour)
• Lab 8 Part 1
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Atoms and Stars
IST 2420
Class 8, March 3
Winter 2008
Instructor: David Bowen
Course web site: www.is.wayne.edu/drbowen/aasw08
Agenda
• Assignments and passbacks
• Contributions of major cultures
• “Expanding circles” – a model of scientific
progress
• Physical Science and natural disasters
• Upcoming assignments
• Lab 8 Part 1: Horizontal Motion
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Contributions of Major Cultures
(to the rise of science) (Q21)
• Prehistoric: attention and observation, e.g.
recording phases of Moon
• Early urban: primarily procedures (recipes)
• Greek: theories, that is idea of theories as
natural explanations
o Frank M. Snowden: role of Blacks as equals
then
• Islamic: preserved Greek science, improved
observations
• Renaissance: united theory and experiment
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Lab 8 Part 2
Dropping objects
• Can from different heights
o Impact increases with greater height (speed),
not weight
• Can and block
o Aristotle said heavier object would fall faster,
in proportion to the weight, because the force is
the weight
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Expanding Circles
What Happens When Science Progresses?
• “Science is Progressive” (two meanings)
• Science always has a boundary
• Science makes progress beyond boundary
o Past discoveries become new tools (barometer)
o Extend theories beyond current experiments
• Important in science, but can be misleading
• Some scientists say that any religion is incompatible
with science, but actually, that is an extension (more)
• Old questions still important; new answers
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Expanding Circles
• After rise of science, most revolutionary
scientific advances (late 19th and 20th
centuries) extend scope, leave core valid (at
least numerically – watch for Quantum
Mechanics later)
1. Newton (our common idea)
2. Special relativity (max speed, energy = mass)
3. General relativity (gravity, creation of space)
4. Quantum Mechanics (uncertainty at atomic
level and smaller)
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Expanding Circles
• “Expanding circles of
knowledge” (DB)
o Exact shape (circle)
unimportant – “blob”
o Science moves boundary
out
o Progresses (expands) by
extending known into
new territory
• Theory and experiment
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Expanding Circles
Review:
• Greek and later science developed isolated
areas of knowledge
o
o
o
o
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Air and water pressure
Speed of light
Falling and sliding objects
Motions of the planets and stars
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Expanding Circles
• Implication #1: eventually, expanding
circles must meet and overlap
o Different approaches, different theories – will
not agree
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Expanding Circles
• Implication #2: circles could meet and fill
the space
o What happens then?
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Natural Disasters #1
• Hurricanes, tornadoes, earthquakes,
tsunamis, mudslides
• Hurricanes best understood
o Rising air over warm ocean – spirals
counterclockwise as seen from above in
Northern Hemisphere due to earth’s rotation
o Picks up water vapor, condenses out higher up
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Natural Disasters #2
• Hurricanes best understood
o When water condenses, air heats again – “fuel”
o Strength: indicated by low pressure in the eye
• No storm, 30” Mercury – if eye gets to 27”, get out
of there! (Katrina)
o Very large size, winds to about 200 mph
o Called typhoons in Asia
• Tornadoes also circular, form over land,
smaller but higher winds (about 300 mph)
o Less well understood than hurricanes
(“supercell”)
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Natural Disasters #3
• Earthquakes
o “Plate Tectonics” gives general explanation
o Earth molten when formed ~ 4.5 BYA
o Cooled, surface condensed into continents (thin
“plates”) floating on molten core (“magma”)
o Currents in core, like currents in boiling water,
carry plates, like the skin on cooking pudding
o Plates crash into each other  earthquakes
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Example:
North & South
America were
joined to
Europe and
Africa, magma
is boiling up at
Mid-Atlantic
Ridge, pushing
them apart.
Geography and
species from
before split
match across
Atlantic ocean
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Natural Disasters #5
• Earthquakes
o As plates crash, tension in “crust” builds up
o  longer time between quakes  larger quake
o Cannot presently tell when quake will happen
• Tsunami – wave formed from underwater
earthquake
o Sensors, warning system, disaster network can
move population out – Hawaii and Alaska
monitoring centers
o No such system in Asian 2004 tsunami, in place
now
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Natural Disasters #6
• Mudslides
o Deforestation and development mean
vegetation on hillsides being cut back
o People living in these areas due to growth in
population
o Heavy rains weaken hillside
o Depth of mud can be hundreds of feet or more
o Can be foreseen, but weak societies cannot act
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Natural Disasters #7
• Natural Disasters
o At present, we cannot predict or control these
o We are learning a lot about them
• Earthquake and hurricane construction codes
• Modern buildings in California much better against
quakes, in Florida against hurricanes
o Prediction will come first, control is a maybe
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For next class
• Next class – in two weeks, on March 17
o WSU Spring Break March 10 - 15
o Reader: “The Planet Mars and Kepler’s Three
Laws of Planetary Motion,” “The Crime and
Punishment of Galileo Galilei”
o Read the manual, Experiment 13 (Parallax)
o Turn in report on Experiment 8 Part 1
• Essay 2 discussion coming up next class
o Summing up the whole semester, does this
course have a core, and if so, what is it?
• Also Questions for Final, Information Sheet
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Lab 8 Part 1
• Rolling carts with good bearings
o Case 1: wheels free to turn
o Case 2: wheels taped so they can’t turn
• Manual says to tape wheels yourself, but
instead swap carts – some will do taped first
• Then wheels free, block on top of cart,
crash into book
• NOT IN MANUAL: Then tape paper air
barrier in back of block, crash again
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For Lab 8 Part 1
• Motion – Aristotle (terrestrial) and Newton
o In many ways, Aristotle and Newton are
opposites here
o Aristotle: without a continuing force (a push),
nothing moves
• Motion stops as soon as push stops
• Coasting is a problem (see next slide)
o Newton: a force causes a change in motion
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• Force necessary to start and to stop
• No force, no change – if at rest (not moving), stay at
rest, but if moving with no force, then no change in
speed or direction
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Terrestrial Motion: Aristotle
• Object only moves if force applied
o Object stops immediately if force stops
• Universe is full
o Air moves out at
front, comes in at back
o Explanation for coasting: air coming in from
back pushes object to keep it moving
o (Today: air actually streams away, vacuum in
back, creates drag)
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…and Newton (1687 A.D.)
• Newton’s Second Law: F = ma
o Force = mass × acceleration
o Acceleration = rate of change in velocity (speed
and/or direction)
o Constant speed in a straight line: no
acceleration, no force
o Inverse also true: no force means no
acceleration, result is no change in velocity =
no change in speed and no change in direction
• “An object in motion tends to stay in motion. An
object at rest tends to stay at rest.”
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