EXAM QUESTION black hole force?

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Homework Help Overview

The discussion revolves around a physics problem related to gravitational forces acting on a star in circular motion around a supermassive black hole. The problem provides specific parameters such as the radius of the orbit and the period of motion, while asking for the magnitude of the gravitational force acting on the star.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to apply the gravitational force formula but notes the challenge of having two unknowns: the force and the mass of the black hole. Some participants suggest using the centripetal force equation and calculating the orbital velocity, while others mention the need for unit conversions.

Discussion Status

The discussion is ongoing, with participants exploring different approaches to the problem. There is an exchange of ideas regarding the methods to find the necessary values, but no consensus has been reached on a definitive solution. Some participants also reference another problem, indicating a broader context of exam preparation.

Contextual Notes

The original poster expresses uncertainty due to the lack of information about the mass of the black hole, which is critical for solving the problem. Additionally, there are references to other problems and resources, suggesting a collaborative study environment.

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EXAM QUESTION black hole force??

Homework Statement



good morning everyone! just getting some last minute studying in before my final exam :(
ran into a question so hoping some one will help me understand it.

A star is observed to be in circular motion about a supermassive black hole at the center of
our galaxy. The radius of this orbit is 10^14 m (no prefix just 10 to the 14), and the period is T=15 years = 4.7 x 10^8s. If this
star has the mass of our Sun (M=2.0 x 10^30 kg), what is the magnitude of the force of gravity acting on it?

A. 4.9 x10^28 N
B. 3.6 x10^28 N
C. 2.0 x10^28 N
D. 1.3 x10^28 N
E. 8.8 x10^27 N
F. 6.5 x10^27 N


Homework Equations



F = (Gm1m2)/r^2
G = 6.7 x 10^-11

The Attempt at a Solution



i started using the formula but we do not know the final force (what we are trying to solve for) OR the mass of the black hole. two unknows and only one equation. i have to be missing something. any help would be great!
thanks
 
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you use the centripetal force equation. mv^2/r. you find v by dividing the length of the orbit (2*pi*r) by T. i think i remember that you have to convert the radius to meters and then convert back to km for the answer.

on a side note, where you able to get problem 16? can you explain how to do that?
 


have not got that far yet.
will look at it now and let you know.
thanks for the help on this problem and good luck on the exam!
 


you too, thanks
 

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