Acceleration, Free-Fall, Early History Flashcards
equations to know
v = >d/>t a = >v/>t df = di + vt OR >x = vt vf = vi + at OR >v = at >x = 1/2 (vi + vf) t OR df = di + 1/2 (vi + vf) t >x = vi t + 1/2 a t2 OR df = di + vi t + 1/2 a t2 vf2 = vi2 + 2ax ht(down/up) = [2x/a ht(down&up) = 2[2x/a
freefall
when an object falls under the influence of gravity alone
gEarth = ?
-9.81 m/s2
What lesson did scientists have to relearn?
They had to relearn that our perception of motion can be influenced by how we observe it.
acceleration
how velocity changes over time
Explain or demonstrate why the unit for acceleration is m/s2
The units are m/s2 because acceleration is the change in velocity over time/per unit time. Velocity has fundamental units of m/s and time has fundamental units of s, so acceleration = change in velocity/change in time yields units of m/s/s. This yields m/s2 as shown below: m/s/s = m/s . 1/s = m/s2
celestial bodies
refer to those things we see beyond the earth, in the “heavens”. moon, sun, planets
What do some of humankind’s earliest recorded observations of motion concern?
concern cycles of sun, moon, stars - daily cycle of sun, 28 day cycle of moon, nightly & seasonal cycle of stars
Instead of a sci analysis, how were the movements of celestial objects explained?
based on religious ideas or primitive analogies with the kind of motions they observed around themselves. Ex: Greeks thought the Sun was a god who rose out of the ocean and drove a chariot across the sky.
When were the 1st telescopes invented?
17th century (1600’s).
What were the early Greeks responsible for? and when?
began developing systems of thought that explained phenomena according to empirical/logical principles vs. religious ideas. 5th & 6th century BC.
two early Greek philosophers
Thales of Miletus & Pythagoras.
Who developed the Greek understanding of motion? When?
Aristotle. 384-322 BC. Athens.
For how long did the Greek understanding of motion dominate Euro thought abt motion?
more than 1000 years
Aristotle’s understanding of motion
I. All objects have a tendency to move toward their “natural” place, depending on what they are made of (earth, water, air, fire) II. The Earth is at the center of the universe & doesn’t move. Sun, Moon, & planets moved in perf circles around earth (constant distance, speed, & direction) III. speed of obj’s to/from earth depended on weight IV. any obj set in motion, on the earth & any rate, will eventually slow & stop. force necessary to keep it moving.
On what was Aristotle’s understanding of motion based?
observations. logic & empirical principles.
problems with Aristotle’s ideas
With observ, obvious tht the planets were sometimes closer to Earth than at other times & tht they moved in their orbits @ varying speeds.
How did Ptolemy try to make the observations of celestial motion fit Aristotle’s theory or explanation of motion?
epicycles. said the planets also revolving in mini orbits. (include diagram of epicycles upon epicycles)
What did epicycles explain?
retrograde motion. planets appeared to move backwards sometimes.
benefits of Ptolemaic system
explained curious motions of the planets.
allowed for the prediciotn of the future positions
role of the Catholic church in promoting Ptolemy’s & Aristotle’s understanding of the structure of the universe
regarded by Church as “authorities” who, tho they lived in the pre-Christian era, had put foward doctrines that contained divine wisdom. scholars who questioned these authorities might have publications of their books prohibited, or even been imprisoned/executed
Why were philosophers, scientists, & Christian scholars distrubed by Ptolemy’s system (geocentric w/ planets orbiting on 1/more epicycles)?
made the system jury-rigged, like a clunky machine fitted out w/ additional parts just to make it work properly. lacked the elegance & simplicity that even the Christian scholars thought God’s work should reveal.
Who was William of Ockham, when was he alive, and what was his important philosophical & scientific principle?
Franciscan monk & Oxford scholar. 1285-1349. “entities must not be needlessly be multiplied”
Ockham’s/Occam’s razor
when consdiering competing explanations, one chooses the simplest explanation (the one w/ the fewest assumptions) & is supported by evidence. when considering an explanation, u should suspect that it’s false if it needs assumption/extra parts added to it over time to fit new data.
