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TBR example 2.9a (book 1):

When a planet orbits the sun, a force acts upon it that depends on its orbital radius. How does the resulting tangential speed of the planet relate to the radius, assuming that the orbit is essentially circular?

A. The speed is inversely proportional to the square root of the orbital radius

B. the speed is directly proportional to the orbital radius

C. The speed is inversely proportional to the orbital radius

D. The speed is inversely proportional to the square of the orbital radius

So I'm looking at equation:

F=ma where a= v^2/R

F= m(V^2/R)

Then here, I multiply out F=(mV^2/R), multiply both sides by R and take the square root, those look directly proportional to me but the book gets V proportional to root (1/R)!

Can anyone help? Thank you!