How did the Ptolemaic model explain the apparent retrograde motion of the planets?
A) The planets moved along small circles that moved on larger circles around Earth.
B) The planets sometimes stopped moving and then reversed to move backward along their circular orbits.
C) The model showed that apparent retrograde motion occurs as Earth passes by another planet in its orbit of the Sun.
D) The planets resided on giant spheres that sometimes turned clockwise and sometimes turned counterclockwise.
A
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What is the angular speed of the ball, in rad/s, as it swings through its lowest point?
What is the wavelength of an electron in the n = 2 state of the hydrogen atom?
a. 
b. 
c. 
d. 
e. 
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