SCI1010 C2

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Information about SCI1010 C2

Published on November 13, 2007

Author: Arkwright26


The Sciences- An Integrated Approach By Trefil & Hazen Prepared by: Long Nguyen, Ph.D. Curry College, Milton:  The Sciences- An Integrated Approach By Trefil & Hazen Prepared by: Long Nguyen, Ph.D. Curry College, Milton Chapter 2 The Ordered Universe To think and ponder: Why do planets appear to wander slowly acros the sky?:  To think and ponder: Why do planets appear to wander slowly acros the sky? Great Idea: Newton’s laws of motion and gravity predict the behavior of objects on Earth and in space. Basic Premise::  Basic Premise: Cause and effect Predictability Sun is up; temperature rises. Turn the key in the car; the engine starts. Flip the switch; the light comes on. Fall, Winter, Spring, Summer, and then Fall. The night sky. The Night Sky:  The Night Sky Before 19th century development of artificial lightings, nights were jet-black full of brilliant stars. Intellectuals studied movements of sun, moon, planets, and stars. Basic Tenet of Science: Physical events are predictable and quantifiable. Scientific Achievements:  Scientific Achievements Stonehenge-built, circa 2800BC, to mark passage of time – Salisbury Plain, England Discovery of spread of disease – John Snow, a London physician, early 1800’s,linked spread of Cholera to hand-pumps of drinking water fountain. Who were the Stonehenge’s builders? Who could move the 50,000kg stones? Ockham’s razor: “Postulates must not be multiplied without necessity.” The Birth of Modern Astronomy:  The Birth of Modern Astronomy Star-filled night sky Stars move in arcs centered on the North Pole star. Fixed form, closely spaced groups are called constellations: Big Dipper and Leo. Moon and planets. Meteors. What causes these objects to move? Ptolemy and Copernicus:  Ptolemy and Copernicus C. Ptolemic (Greek, 200AD)model: Earth at center, stars and planets revolved around it in concentric circles. Lasted almost 1500 years N. Copernicus (Pole, 14-1500AD) model: Sun at center instead of Earth Observations: Tycho Brahe & Johanes Kepler Improved instrument Carefully recorded data Thorough analysis –> Kepler’s first law: planets orbit the sun in elliptical orbits. The Birth of Mechanics:  The Birth of Mechanics Branch of science that deals with the motions of material objects. Galileo Galilei (Italian, 15-1600) jailed by the church for supporting Copernican model. 1992, the church reverse the guilty verdict. Reason: original judges had not separated questions of faith from questions of scientific fact. Speed vs Velocity:  Speed vs Velocity Speed: v (m/s) = d (m) /t (s) Velocity: vector: speed + direction Example: Car travels at 30mph due North How many miles will it go in 10 min? d = ( 10/60 h) *30 mph = 5 miles Acceleration: Change in velocity – a (m/s2) = ( v.f – v.i) (m/t) / t (s) Accelerate vs. Decelerate (accelerate backward) Galileo’s Falling Ball Exp. :  Galileo’s Falling Ball Exp. Fig 2-7 p.41: recording time vs. distance Any object accelerating on Earth, falls with same constant acceleration: Velocity (m) = constant a (m/s2) x time (s) v = a x t When free fall, a = g = 9.8 m/s2 ( or 32 ft/s2) d = ½ x a (m/s2) t 2 (s2) Examples:  Examples Sprinter gains the speed of 20m/s in 2 second What is his acceleration? How far does she travel during this 2 sec? Assuming she maintains the remaining distance at same speed. What will be her time of the 100 meter race? Extreme acceleration:  Extreme acceleration On Earth - 1g In Cars, amusement park rides – up to 2g Pilot: 4-8g Centrifuge: 8g’s Isaac Newton and Universal Laws of Motion:  Isaac Newton and Universal Laws of Motion First Law: Moving object will continue moving in straight line at constant speed. Stationary object will remain at rest. Uniform motion - innertia Acceleration – changed by force Acceleration produced on a body by a force is proportional to the magnitude of the force and inversely proportional to the mass of the object Force = Mass x Acc (f = m*a) Isaac Newton and Universal Laws of Motion:  Isaac Newton and Universal Laws of Motion Third Law: For every action there is an equal and opposite reaction. Pushing the wall Car hits tree Newton laws at work:  Newton laws at work Boy on skates throwing a stack of baseball. Fish swims. Rocket flies. Momentum:  Momentum Moving train Speeding bullet Linear momentum: Momentum (kg-m/s) = mass (kg) x velocity (m/s) p = m*v Conservation of Linear Momentum:  Conservation of Linear Momentum Second Laws: no external forces act on the system, change in total momentum of the system is zero. Rolling soccer ball Fireworks Angular Momentum:  Angular Momentum Rotating top Rotating wheel Torque: twisting force act on rotating object Figure Skater Universal Force of Gravity:  Universal Force of Gravity Attraction force between objects Earth & Moon Earth and people F = ( G x Mass1 x Mass2 ) / distance2 G = 6.67 x 10-11 (m3/s2-kg) or N-m2/kg2 N: Newton – unit of force Weight and Gravity:  Weight and Gravity Depending on where you are, you weight differently

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