David S. answered • 11/03/19

Experienced AP Chemistry/Physics Teacher (HS thru College)

This is a clever question. You're right that the answer is not zero. Even if the speed is constant, there is a centripetal or radial acceleration due to the constant change in direction. The equations that relate to centripetal acceleration are a_{c}=v^{2}/r or a_{c}=ω^{2}r. (v=2πr/T and ω=2π/T, where T is the orbital period = 365.25 days = 3.16x10^{7}s) Now it's just a matter of "Googling" the radius of the Earth's orbit and plugging into either equation (or both to prove to yourself that you did it correctly).