Astronomy Picture of the Day

Astronomy Picture of the Day

Something Cool Einstein Ring

Something Cool Einstein Ring

Something Cool Einstein Ring

Astronomy 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 raised

Key Ideas What do forces do? How does the force of gravity depend on mass and distance? How does gravity cause orbits?

Forces change an object's motion (The) Force

Is 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. Y

Newton's First Law What happens if there is no net force?

Newton's First Law What happens if there is no net force? NOTHING Newton'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 force

What 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 object b)a less massive object

Newton's Second Law CT: Which is harder to accelerate? a)a heavy object A light object Force = 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/appar

Newton's Third Law For 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.

Energy When you apply a force to an object over a distance, you change its Energy Kinetic Potential Thermal

Conservation of Energy Energy changes forms but is never lost /Users/charlottechristensen/Desktop/Astro101/Tex

Newton'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 should a)throw the hammer at the spaceship to ge someone's attention b)throw the hammer away from the spaceship c)use a swimming motion with your arms d)kiss your ship good bye

Our Favorite Force: Gravity

Gravity Mass Attracts Other Mass

Newton's Universal Law of Gravity

CT: 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 orbit Users/charlottechristensen/Desktop/Astro101/Texbook/Applets/chapter04/orbit_t

Gravitational Orbits

Gravitational Orbits CT: If one could magically turn off gravity from the Sun, what would the Earth do? Please draw a diagram to illustrate it

Gravitational Orbits CT: If one could magically turn off gravity from the Sun, what would the Earth do? Please draw a diagram to illustrate it

Gravitational Acceleration More massive objects have more gravitational force

Gravitational Acceleration More massive objects have more gravitational force But More massive objects are stronger to move

Gravitational Acceleration More massive objects have more gravitational force But More massive objects are stronger to move The mass cancels out Gravitational acceleration is independent of mass

Escape 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.htm

Escape 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 velocity b) Less than the Earth's escape velocity c) The same as the Earth's escape velocity d) Cannot be compared to Earth's with this information

Escape 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 velocity b) Less than the Earth's escape velocity c) The same as the Earth's escape velocity d) Cannot be compared to Earth's with this information

Assigned 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 class?