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Math Help - Need to understand how they solved this problem

  1. #1
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    Need to understand how they solved this problem

    Below is the answer to a problem. I cannot figure out how they did it I tried to start with the math but hit a dead end.

    Any help would be great:

    I am unable to figure out how they did the following problem, I see where they substitute in for ay, and I am fine there.







    I dont understand the steps they took to get the answer below:







    I tried the following:




    After this point I kept running into some walls I tried factoring out a negative, and I tried a few other things but I am not doing something right as its not coming up like it should so I must be missing a rule or not using it correctly.


    thanks,

    Brian
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  2. #2
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    Quote Originally Posted by wilder7bc View Post
    Below is the answer to a problem. I cannot figure out how they did it I tried to start with the math but hit a dead end.

    Any help would be great:

    I am unable to figure out how they did the following problem, I see where they substitute in for ay, and I am fine there.







    I dont understand the steps they took to get the answer below:







    I tried the following:




    After this point I kept running into some walls I tried factoring out a negative, and I tried a few other things but I am not doing something right as its not coming up like it should so I must be missing a rule or not using it correctly.


    thanks,

    Brian
    Hi Brian,

    Solving, we get

    m_1\left(g+\frac{m_2-m_1}{m_1+m_2}g\right)=m_1\left(\frac{g(m_1+m_2)+g(  m_2-m_1)}{m_1+m_2}\right)

    =m_1\left(\frac{2gm_2}{m_1+m_2}\right)
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  3. #3
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    Quote Originally Posted by Archie Meade View Post
    Hi Brian,

    Solving, we get

    m_1\left(g+\frac{m_2-m_1}{m_1+m_2}g\right)=m_1\left(\frac{g(m_1+m_2)+g(  m_2-m_1)}{m_1+m_2}\right)

    =m_1\left(\frac{2gm_2}{m_1+m_2}\right)

    Well my physics book gave me the answer as this:




    The book states the answer is:




    I dont understand how they got to that answer or the math and rules involved.

    The answer your giving me is not the same as the book does. I dont really need the answer as I have it already from the book.

    I need to know how the book came to get their final answer.



    Thanks for assisting, but I am just after the rules and math that they used to get their answer.

    If you could show me that would be awesome as I am trying to move onto the next problem but I am one of those people who obsess when I dont understand something and its so hard for me to move on to the next physics problem as I have problems letting go lol

    Thanks,

    Brian
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  4. #4
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    Yes, just multiply my last step out,

    m_1\left(\frac{2gm_2}{m_1+m_2}\right)=\frac{m_1}{1  }\ \frac{2gm_2}{m_1+m_2}=\frac{2gm_1m_2}{m_1+m_2}

    =\left(\frac{2m_1m_2}{m_1+m_2}\right)g
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  5. #5
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    Quote Originally Posted by Archie Meade View Post
    Yes, just multiply my last step out,

    m_1\left(\frac{2gm_2}{m_1+m_2}\right)=\frac{m_1}{1  }\ \frac{2gm_2}{m_1+m_2}=\frac{2gm_1m_2}{m_1+m_2}

    =\left(\frac{2m_1m_2}{m_1+m_2}\right)g
    Awesome thanks!

    Brian
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  6. #6
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    oh wow

    I just went back and looked at that and I missed that entire thing because I didnt finish out my math. I was so busy looking for some difficult rule that I missed addition of fraction and multiplying it out to finish up.

    egads!!!! thanks again.

    Brian
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  7. #7
    Member Miss's Avatar
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    Quote Originally Posted by wilder7bc View Post
    Below is the answer to a problem. I cannot figure out how they did it I tried to start with the math but hit a dead end.

    Any help would be great:

    I am unable to figure out how they did the following problem, I see where they substitute in for ay, and I am fine there.







    I dont understand the steps they took to get the answer below:







    I tried the following:




    After this point I kept running into some walls I tried factoring out a negative, and I tried a few other things but I am not doing something right as its not coming up like it should so I must be missing a rule or not using it correctly.


    thanks,

    Brian
    Post the whole problem to make our life easier.
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  8. #8
    Member Miss's Avatar
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    Oops.
    I did not see the other replies
    Sorry :O
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