# the issac physics astronomy question

https://isaacphysics.org/questions/binary_star_system_num?board=spc_china_a3&stage=all
I complete the first one but have no idea about the second question
i worked out the part a question by myself throght searching some relative information but the second question is too ticky i cannot have any solution can you help me a little
https://isaacphysics.org/questions/binary_star_system_num?board=spc_china_a3&stage=all
Original post by laoke
https://isaacphysics.org/questions/binary_star_system_num?board=spc_china_a3&stage=all
I complete the first one but have no idea about the second question

Original post by laoke
i worked out the part a question by myself throght searching some relative information but the second question is too ticky i cannot have any solution can you help me a little
https://isaacphysics.org/questions/binary_star_system_num?board=spc_china_a3&stage=all

Hi, I understand that you are new to TSR. Welcome to TSR!
Please do not post the same question multiple times and also provide us with more info on what you have tried or what you are stuck with.
It would be good to read the guidelines here, too.

Some guides for part B.
Write the KE of each star in terms of the gravitational potential energy. We can do this by writing the gravitational force between the 2 stars equal to the centripetal force of star mass, m and do the same to the other star.
but if the the gravitational force between the 2 stars equal to the centripetal force of star mass, the only conclusion I can get is the velocity of m1planet and velocity of m2 planet are different.m1v^2÷r=Gm1m2÷r^2
anyway the two planet should ave same velocity I think but through this calculation the velocities are different
Original post by Eimmanuel
Hi, I understand that you are new to TSR. Welcome to TSR!
Please do not post the same question multiple times and also provide us with more info on what you have tried or what you are stuck with.
It would be good to read the guidelines here, too.

Some guides for part B.
Write the KE of each star in terms of the gravitational potential energy. We can do this by writing the gravitational force between the 2 stars equal to the centripetal force of star mass, m and do the same to the other star.

sorry the system said my previous two are omitted which cannot be published so I tried for three times. I would aviod next time
Original post by laoke
but if the the gravitational force between the 2 stars equal to the centripetal force of star mass, the only conclusion I can get is the velocity of m1planet and velocity of m2 planet are different.m1v^2÷r=Gm1m2÷r^2 ...

Let's say the inner star is labelled with mass m1 while the outer star is labelled with mass m2.
The centripetal force of m1 is NOT m1v^2÷r.

Indeed, the velocities of m1 and m2 are different but they are undergoing circular motion with a common centre, so there is a common quantity related to their circular motions.

The object in question is star NOT planet.

If you have done part A "properly", this part is not much different.
Original post by Eimmanuel
Let's say the inner star is labelled with mass m1 while the outer star is labelled with mass m2.
The centripetal force of m1 is NOT m1v^2÷r.

Indeed, the velocities of m1 and m2 are different but they are undergoing circular motion with a common centre, so there is a common quantity related to their circular motions.

The object in question is star NOT planet.

If you have done part A "properly", this part is not much different.

you are true I have done the part A by accidently rearrange some equations.
perhaps this question is not propociate for me. sorry to distrub you
Original post by laoke
you are true I have done the part A by accidently rearrange some equations.
perhaps this question is not propociate for me. sorry to distrub you

If you think you have done Part A by rearranging some equations, it would be good that you make an effort to understand the rationale of writing the equations for this question.

If you are taking A-level Physics, this question can appear in any A-level Exam boards.