Which of the following observations support Aristotle’s
geocentric model? Select all
statements that apply.
A. The sun, moon, and stars
appear to follow a circular
path through the sky.
B. The sun and moon appear
to be the same size and
brightness as the stars.
C. The sun, moon, and stars
seem to move at the same
rate across the sky.
D. For people on Earth, the
planet does not feel like it
is moving.
E. Some planets appear to cross
between the sun and Earth.
F. Some planets appear to pass
behind and beyond the sun.

Cyclotrons are widely used in nuclear medicine for producing short-lived radioactive isotopes. these cyclotrons typically accelerate h- (the hydride ion, which has one proton and two electrons) to an energy of 5 mev to 20 mev. this ion has a mass very close to that of a proton because the electron mass is negligible—about 1 2000 of the proton’s mass. a typical magnetic field in such cyclotrons is 1.9 t. (a) what is the speed of a 5.0-mev h-? (b) if the h- has energy 5.0 mev and b = 1.9 t, what is the radius of this ion’s circular orbit?