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Published byColeen Blake Modified over 6 years ago
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Day 45 In AP Physics 1) You remember that you are actually in physics class 2) We remind ourselves of all that gravity stuff and density 3) Gravitational Potential, Orbits 4) Centripedal
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REMINDER SO FAR
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REMINDER SO FAR
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Important things to remember
There is a difference between the FIELD strength overall vs. the FIELD strength compared to Earth Ex: A field strength of 25 is 2.5x Earth’s value.
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Expectations Try a-c on the handout so far, then STOP THERE! Alone!
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Now try the rest D-f would you kindly?
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First, look at the axis, and don’t freak out when you see something unusual.
Major idea: How can we relate 1/r2 to g? A way to think about it: Substitution
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What did we do? We KNEW that the graph of g vs. r is independent of mass. Therefore g is related to r by a factor of 1/r2. That is the shape of the graph. All we had to do is SCALE it appropriately. You will be doing MANY graph things like this for me on all topics.
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And for F: We want MASS, all we have is g and 1/r2.
When it comes to graphs, there are 3 things we can do: 1) II) III) Look at the equation and which is best?
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Slope!
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What did we do? We RELATED the axis to the equation
We turned a 1/x2 graph into a linear graph by equation manipulation We related the two axis in the equation to see if they multiply (AREA) or divide (SLOPE)
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Take a look at
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Thoughts “The distance between the objects goes from R to 3R”
True or false? FALSE: From 2R to 6R due to being from center of mass
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“Tripling the radius increases the mass of each sphere by 3”
Thoughts “Tripling the radius increases the mass of each sphere by 3” True or false? FALSE: With the same density, it depends on R3 from the sphere volume. 33 is 27 times the mass
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“So the system mass increases by 27 times” True or false?
Thoughts “So the system mass increases by 27 times” True or false? FALSE: Each goes up by 27 times!
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Lets determine it
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Now to Orbits: Look here Idea: At slow speeds, the ball will simply fall back and hit Earth. Idea: At the ORBITAL VELOCITY at that height, the ball will have a CIRCULAR orbit Idea: At a velocity HIGHER than the ORBITAL VELOCITY but less than the ESCAPE VELOCITY, the ball has an ELLIPTICAL orbit Idea: At higher velocities, it escapes Earths ‘Gravity Well’
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AND THE MAJOR LINK In each case, the ball is ‘falling’ towards Earth due to the gravitational pull. But at too high speeds, the downward pull is not enough to overcome its inertia tangential
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A blast… Try HW 1 for me
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