Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Astronomy Picture of the DaySomething Cool – Einstein RingSomething Cool – Einstein RingSomething Cool – Einstein RingAstronomy News Article●Read an interesting astronomical news article from spaceref.com OR space.com●Turn in a typed handout with –1 – 3 paragraphs summarizing–1 – 2 questions raisedKey Ideas●What do forces do?●How does the force of gravity depend on mass and distance?●How does gravity cause orbits?(The) Force●Forces change an object's motionIs there a net force?●A car coming to a stop.●A bus speeding up.●An elevator moving up at constant speed.●A bicycle going around a curve.●A moon orbiting Jupiter.Is there a net force?●A car coming to a stop. Y●A bus speeding up. Y●An elevator moving up at constant speed. N●A bicycle going around a curve. Y●A moon orbiting Jupiter. YNewton's First LawWhat happens if there is no net force?Newton's First LawWhat happens if there is no net force?NOTHINGNewton's First Law: An object at rest tends to stay at rest and an object in motion keeps the same velocity unless acted on by a forceWhat forces are acting on:●A falling ball?●Me?●A ball on a string, swung in a circle?Newton's Second Law●CT: Which is harder to accelerate?a)A more massive objectb)A less massive objectNewton's Second Law●CT: Which is harder to accelerate?a)A heavy objectA light objectForce = Mass X Acceleration(F = ma)Mass Versus Weight●Mass is intrinsic to an object●Weight is a measurement of the (gravitational) force on an object/Users/charlottechristensen/Desktop/Astro101/Texbook/Applets/chapter04/apparentWeight.htmNewton's Third LawFor any force, there is an equal and opposite reaction force●What is the reactive force to my weight?●What is the net force that I feel?CT: Is the force the Earth exerts on you larger, smaller, or the same as the force you exert on it? a)Earth exerts a larger force on you. b)I exert a larger force on Earth.c)Earth and I exert equal and opposite forces on each other.CT: Is the force the Earth exerts on you larger, smaller, or the same as the force you exert on it? a)Earth exerts a larger force on you. b)I exert a larger force on Earth.c)Earth and I exert equal and opposite forces on each other.EnergyWhen you apply a force to an object over a distance, you change its Energy●Kinetic ●Potential●ThermalConservation of Energy●Energy changes forms but is never lost/Users/charlottechristensen/Desktop/Astro101/Texbook/Applets/chapter04/cannonball_orbit_fire.htmNewton's Laws●CT: You are an astronaut taking a space walk to fix your spacecraft with your hammer. Your lifeline breaks and the jets on your back pack are out of fuel. To return safely to your spacecraft you shoulda)Throw the hammer at the spaceship to ge someone's attentionb)Throw the hammer away from the spaceshipc)Use a swimming motion with your armsd)Kiss your ship good byeOur Favorite Force: GravityGravityMass Attracts Other MassNewton's Universal Law of GravityCT: Strongest gravitational force?Weakest gravitational force?a)b)c)CT: Newton's Universal Law of Gravity●If the mass of the Earth were to double, how would your weight change?●If the radius of the Earth were to double, how would your weight change?●If the radius of the Sun were to change how would the gravitational force on the Earth change?Gravitational Orbits●Gravity can hold things in orbitUsers/charlottechristensen/Desktop/Astro101/Texbook/Applets/chapter04/orbit_trajectory_cannonball.htmGravitational OrbitsGravitational Orbits●CT: If one could magically turn off gravity from the Sun, what would the Earth do?–Please draw a diagram to illustrate itGravitational Orbits●CT: If one could magically turn off gravity from the Sun, what would the Earth do?–Please draw a diagram to illustrate itGravitational Acceleration●More massive objects have more gravitational forceGravitational Acceleration●More massive objects have more gravitational forceBut●More massive objects are stronger to moveGravitational Acceleration●More massive objects have more gravitational forceBut●More massive objects are stronger to moveThe mass cancels outGravitational acceleration is independent of massEscape Velocity●How fast you have to throw an object so that it escapes the Earth's gravitational field/Users/charlottechristensen/Desktop/Astro101/Texbook/Applets/chapter04/cannonball_orbit_fire.htmEscape Velocity●CT: Planet X is both smaller and more massive than Earth. The escape velocity of planet X will be a) Greater than the Earth's escape velocityb) Less than the Earth's escape velocityc) The same as the Earth's escape velocityd) Cannot be compared to Earth's with this informationEscape Velocity●CT: Planet X is both smaller and more massive than Earth. The escape velocity of planet X will be a) Greater than the Earth's escape velocityb) Less than the Earth's escape velocityc) The same as the Earth's escape velocityd) Cannot be compared to Earth's with this informationAssigned●Reading (due Tues in class)–Ch 2 -- “Discovering the Universe for Yourself”–Ch 3.1, 3.2, 3.3 – “The Science of Astronomy”●TWO questions on the textbook, ONE on the lab (due Tues, 8:00 am)–Email to Jeff and me with READING QUESTION in the subject line●Lab 2 (due Tues in class)●Stop by office hours (due Tues, 5:00pm)●First news article summery (due Tues. in class)Minute Writing●What was the most difficult concept in today's
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