atoms and stars ist 2420 and ist 1990 class 6: february 16 fall 2005 david bowen * slides 12 and 15...

Atoms and StarsIST 2420

and IST 1990http://www.is.wayne.edu/drbowen/aasW05

Class 6: February 16

Fall 2005

David Bowen* Slides 12 and 15 changed to show what happened in class

2/16/05 Atoms and Stars, Class 6 2

Lab Room

• Seems that there may be outsiders playing in the lab room when we are in classroomo May be equipment missing

• Lab room will be locked when none of us are inside

• I will keep door so it is locked when closed

• Please close door when last person leaves


DIS Free Tutoring

• Math• Writing• Call 313-577-0832

• Also Writing Center 2310 Undergraduate Library.o Call 313-577-2544 for questions/appointment


Handouts• PowerPoint notes

• Early Assessment grades (see slide 8)

• Passbacks

Names• Initial by your name on signin list

• Go through class names again


Due this week• Assignments go in the “IN” folder

• Report for Lab 3A (Inclined Track #2)

For next week…• Reader Pp 80 - 89 & 157 - 163

• (Manual Pp 35 – 41, Experiment 8)

• Turn in Report for today’s Lab 3 Part 3

• Midterm: March 9, Questions for Midterm


Writing Assignments by Hand?

• Legible!

• Will be checked for grammar and spelling as if you were using a word processor


Late Assignments (Repeat)• OK, there is a penalty for late assignments –

they may not be turned back quickly

Missed Class Makeup (Repeat)• Class: a one page summary of the class.

Strict page limit. This makes it hard.

• Lab. Photocopy of data sheet, together with your write-up for experiment


Early Assessment grades• Turned in February 16• -T: attend 2 or fewer classes out of 5• -H: submit 2 or fewer assignments out of 5• Result in letter from University if not “OK”• Early Assessment grades do not count in

course grade, do not go on transcript – warning only

• IST 1990: -H: 3 or fewer postings-T: not in class for Moodle


Experiment 3 grades• Hypothesis to be tested: s = kt2 (Ex: k =¼)

• Are dividedtimes equalto eachother?o Accuracy?o This is the

test of thehypothesis!!!

Time Dist. Divide Time by

Divided

Time

2 1 1 2

4 4 2 2

6 9 3 2

8 16 4 2


Experiment 3 (Cont’d)1. Measure times down track, repeat

measurements2. Average times for each distance

• Average: total divided by # of things totalled

3. (generally not done) Divide A0-B1 avg. time by 1, A0-C4 avg. by 2, A0-D9 avg. by 3, A0-E16 avg. by 4.

4. Are divided averages equal, within error?If so, then distance increases as time2


Experiment 7 grades• People getting mixed up on how to do the

calculations (too long a time has passed?)• Weight of displaced water = weight of glass

and water with object in water – weight of water without object in watero “Cleaner” to take object out, fill to line with

water, but OK

• Density = weight of object / weight of displaced water


Questions for Midterm #1

• “What is the difference between procedures, data, and observations, hypotheses, and theories? Describe an example of each from one of the labs.”o You may be told which labo You may be given a new example


Questions for Midterm #18

• What is meant when people say that science is progressive? What types of progress can be involved? Give examples from this course, including:o New scientific knowledge being developedo Old discoveries become new techniques

• Both updated on course web site


If science is progressive…

• Will science ever reach the absolute truth?

• Will science ever approach the absolute truth asymptotically (as close as you want as long as that is not zero)?

• New results still appearing

• Domain of science has so far been expanding


Weight on a Mountaintop

• Does an object weigh more (in air) on a mountain top than at the bottom?o Yes. Object weighs less by the weight of

displaced air. It displaces the same volume of air, but air is less dense on top of the mountain.

• Pressure is less so air expands

• Water (fluids) do not compress and expand (at least not very much)


Weight on Mountaintop (cont’d)

• 25 lb weighto In water, displaces 3.16 lb (~ 3 lb 3 oz)o In air, displaces .0041 lb (~ 1/20 oz) at STP,

small enough that we usually neglect it

• Less dense than water? Then floats in water.o Oil and gasoline float in water

• A gas that is less dense will “float up” in a gas that is more dense


Science and Religion• Question has come up: what am I saying about

science compared to religion?• Belief in science: quote from Ruse, Can a

Darwinian be a Christian? (aggressive)• I do belong to a church, very liberal: Birmingham

Friend’s Meeting – Quakers.o Science does not answer all questions for which we

need answers, cannot explain all that we observe. (yet?)

• Further sources of conflict will appearo Physical Science, Life Science, Cognitive Science


Density as Demo• Bigger objects – one sinking, one floating• Volume of displaced water = volume of

object (Archimedes)• Different method for measuring weight of

displaced water – remove it to bottle• Accuracy of measurement – estimate by

repeating measurements• Null hypothesis – if difference is within

accuracy, cannot say it is different than zero


Density as Demo (cont’d)

• Specific gravity =weight of object ÷ weight of displaced water.o no units, since it is weight divided by weighto also = object’s density ÷ water’s densityo water’s density = 1 gm / cm3, so specific gravity

of an object = its density in gm / cm3

o (cm3 is common abbreviation for cubic centimeter)



• Null hypothesis: if two quantities are equal within their accuracies, they are effectively equal



Observations (lb and oz)Wood

• Object weight in air: __________

• Weight of displaced water: __________

• Fraction of wood under water:__________



Analysis (use Excel spreadsheet)Wood

• Specific gravity: __________

• Fraction of wood under water:__________



• Pressure at a depth = weight of the column of water aboveo Pressure increases with depth because there is

more water aboveo An object weighs less in water because greater

water pressure on pushing up on bottom compared to lesser on top pushing down

Theory:



Complicated Simple


Readings (The Visible Stars)• Motions of bodies in sky known to all

civilizations• Constellation: groups of stars, pattern

invariant over human lifetimeo 88 total constellations, Zodiac is 12 of these

• Angular measuremento Degrees: 360° = circle (horizon), 90º horizon to

pole. Fist at arm’s length ~ 10°, finger ~ 1ºo Minute ('): 60' = 1°o Second ("): 60" = 60'


The Visible Stars (cont’d)

• Stars circle around pole (Pg 93)o Really, earth is turning underneath starso 360º in 24 hrs = 15º/hr

• Also move annually relative to sun

• Five visible planets Mercury, Venus, Mars, Jupiter, Saturn move with respect to starso Uranus, Neptune, Pluto require telescope



• Planets move through stars west to east like sun and moon, but periodically reverse or retrograde motiono Mercury, Venus stay close to sun (morning &

evening stars)• Retrograde when close to but farthest east of sun,

reappear west of suno Mars, Jupiter, Saturn roam with respect to sun

• Retrograde when opposite sun



• Suno Highest in sky at Summer Solstice (~June 21,

most daylight)o Lowest at Winter Solstice (~December 21,

longest night)o In between Spring and Vernal (Fall) Equinoxes

– equal day and nighto Reversed in Southern Hemisphereo Also moves east with respect to stars



• Suno As sun moves through stars, traces plane called

“ecliptic”o Moves through 12 constellations of Zodiac


The Visible Stars (cont’d)• Moon

o Rises in east, sets in west like suno Also moves to the east with respect to starso New moon – moon between earth and suno Full moon – earth between sun and moon

• Eclipseso Moon eclipses sun, orbit tilted so rareo Lunar eclipse when earth’s shadow hides full

moon


New “planets”

• Pluto discovered 1930, orbit radius ~30 AU• Quaoar discovered 2002, ~1/8 size of Pluto

o 42 AU from sun (42 × radius of earth’s orbit)• Radius of earth’s orbit = 93 million miles

• 2003 VB12 (“Sedna”) ~ size of Plutoo Orbit radius ~ 39 AU

• 2004 DW ~½ size of Plutoo Orbit radius ~45 AU


New “planets” (cont’d)

• Quaoar, Sedna and 2004 DW may not be planets. Definition of a planet is in dispute. Also cast doubt on whether or not Pluto is a planet

• These 3 are in or near the Kuiper Belt, belt of asteroids


What are these things? (modern)

• Star – source of light (gravity has crushed atoms to start nuclear reactions)

• Planet – large, opaque, nonluminous, circles a star (Pluto is on the smallish side)

• Moon – a natural satellite of a planet• Asteroid – Small planet, size from 1 km (.6 mi) to

1,000 km (620 mi)• Comet – Few km, frozen ice & rock, elongated

orbit, vaporizes when near sun, makes tail


Measurements

• Physical Science (Physics, Chemistry, Astronomy) now has mathematical theories that make numerical predictions that are checked against measurementso Exception is Geologyo Earlier, mostly qualitative theories checked

against observations (some mathematical)

• Life sciences currently mostly qualitative


Measurements (cont’d)• Measurements have accuracy, must check

how accurately your measurements areo Repetition is a good methodo Results agree with theory if they are within

measurement accuracy

• Why are Life Sciences not mathematical?o Started later?o More difficult, takes longer?o A different type of science?


Lab

SPER stopwatchesmeasure minutes,seconds and hundredthsof seconds.


Lab (cont’d)• Projectiles (Part C), Pp 11 & 12

o Follow directions hereo Measure distances back from where the rubber

band is relaxed (see figure on Pg 11)o Accept level start only - reject trials in which

projectile starts out angling upwardso When repeating, do not repeat setup in #1o Step 1, “immediately below” – how do you do

this?


Lab (cont’d)• Projectiles (Part C), Pp 11 & 12

o Horizontal distance – how wide are the floor tiles?

o Consider null hypothesis – no difference

ISP 3360 – break time

ISP 3340 starts


ISP 3340

• Pictures for Moodle?

• Postings in Moodle – need to get going

• Other articles on course web site – password needed

• Essay 1 on Rocks of Ages and other articleso Due February 23, next weeko Title page must list topic and descriptive title

End for ISP 3340

Lab

atoms and stars ist 2420 and ist 1990 class 6: february 16 fall 2005 david bowen * slides 12 and 15...

Documents

class names againatoms

water weight of water

fewer assignments

weight of glass

writing assignments

divided times equal

todays lab

lab roomseems