Return to MCAT® Blog
Homepage
MCAT Physics Question — Satellite Orbit
- by
- Oct 23, 2014
- MCAT Question of the Day
- Reviewed By: Liz Flagge
A satellite of mass ms is orbiting a planet at a speed vs. The planet has a mass Mp. Which of the following represents the radius of the satellite’s orbit measured from the center of the planet?
A) GMp / vs2
B) √(GMpms / vs)
C) ½ (msvs2)
D) Gms / vs2
Explanation
An object travelling in circular orbit is experiencing a centripetal force from the planet’s gravity. We may thus set up the following equation:
Fc = GMpms / r2 = msv2 / r
Cancelling the mass of the satellite we get:
GMp / r2 = v2 / r
Multiply both sides by the radius of the orbit:
GMp / r = v2
The question asked for the radius of the orbit, so isolate r:
GMp / v2 = r
Thus, choice (A) is the right answer.
If you’re not sure how to proceed, always try to eliminate one or two choices before you guess. If you couldn’t remember the equations for centripetal force or for gravity, you may still have been able to recognize choice (C) as the kinetic energy equation. The question asked you for radius, so an answer choice that would be in joules would have to be wrong. So eliminate (C) and guess.
Want more MCAT practice?
We’ve got options for every schedule and learning style!
From the best online MCAT course created by top instructors with 524+ MCAT scores to the most representative full-length practice exams and private tutoring, we can custom tailor your MCAT prep to your goals!
Not sure which option is right for you? Schedule a free MCAT consultation with an MCAT expert using the form below. No obligation, just expert advice.
Related Posts
Search the Blog
Free Consultation
Interested in our Online MCAT Course, One-on-One MCAT Tutoring or Med admissions packages? Set up a free consultation with one of our experienced Senior Student Advisors.
Schedule NowPopular Posts
-
-
MCAT Blog What's on the MCAT? -
-
-
MCAT Blog How to Review MCAT Full Lengths
Free MCAT Practice Account
Need great MCAT practice?Get the most representative MCAT practice possible when you sign up for our free MCAT Account, which includes a half-length diagnostic exam and one of our full-length MCAT practice exams.
Learn More