Chapter 12: Gravity
Warm-Ups



1.  


A planet's orbit around the sun is an ellipse. Consider points A and B on the ellipse. How does the centripetal force exerted on the planet at point A compare to the centripetal force exerted on the planet at point B? How about the potential energies at A and B? Kinetic energies? How about angular momenta?


2.  

Estimate the force that the Moon exerts on you when it is directly overhead.

(You need some data from the book to answer this question.)


3.  

Two different planets are orbiting the same sun along two different orbits. The red orbit is circular, the blue orbit is elliptical. Compare the speeds of the planet in the the blue orbit at points A, B, and E. Compare the speeds of the planet in the red orbit at points C, D and E. The planet in the blue orbit is to be shifted to the red orbit as passes point E. Does it have to speed up or slow down?


4.  

The space commnunication company is planning to take a spy satellite to a spot 35,800 km above the Earth's surface and release into a geosynchronous orbit. ( In a geosynchronous orbit the satellite will orbit at the same rate as the points on the surface of the Earth below it so as to appear to hover over the same spot).
Is this possible?
If yes, how fast must the satellite be moving when it is released?



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