Results 1 to 4 of 4

Math Help - Uniform Circular Motion Problem

  1. #1
    s3a
    s3a is offline
    Super Member
    Joined
    Nov 2008
    Posts
    597

    Uniform Circular Motion Problem

    Here is(are) the question(s):

    "Find the centripetal acceleration for each of the following:
    (a) a point on the earth's equator (ignore its orbital motion);
    (b) the earth in its orbit around the sun;
    (c) the sun's orbit around the center of the Milky Way (period = 2 x 10^8 y; radius = 3 x 10^20 m"

    (Correct) Answers:
    (a) 3.37 x 10^(-2) m/s
    (b) 5.9 x 10^(-3) m/s^
    (c) 3 x 10^(-10) m/s

    I get (a) ac = 2.97 x 10^(-10) m/s^2 which is wrong. What am I doing wrong?

    (My work is attached)

    Any help would be greatly appreciated!
    Thanks in advance!
    Attached Files Attached Files
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by s3a View Post
    Here is(are) the question(s):

    "Find the centripetal acceleration for each of the following:
    (a) a point on the earth's equator (ignore its orbital motion);
    (b) the earth in its orbit around the sun;
    (c) the sun's orbit around the center of the Milky Way (period = 2 x 10^8 y; radius = 3 x 10^20 m"

    (Correct) Answers:
    (a) 3.37 x 10^(-2) m/s
    (b) 5.9 x 10^(-3) m/s^
    (c) 3 x 10^(-10) m/s

    I get (a) ac = 2.97 x 10^(-10) m/s^2 which is wrong. What am I doing wrong?

    (My work is attached)

    Any help would be greatly appreciated!
    Thanks in advance!
    First you do not have enough explanation of what you are attempting to do (as a consequence you will not gain any marks for method even though the final answer is wrong).

    The centripetal acceteration in uniform circular motion is:

    a=r \dot{\theta}^2

    Here r\approx 6.38\times 10^6\ \text{m} is the Earths radius, and \dot{\theta}=(2\pi)/(24 \times 60 \times 60) \approx 7.272 \times 10^{-5} \text{radians/second} the Earths rotation rate.

    so:

    a \approx (6.38\times 10^6)\times (7.272 \times 10^{-5})^2 \approx 0.0337 \text{m/s}^2

    CB
    Follow Math Help Forum on Facebook and Google+

  3. #3
    s3a
    s3a is offline
    Super Member
    Joined
    Nov 2008
    Posts
    597
    Thanks for telling me how to get (a) right but why is my method wrong?(Bad logic or bad formula or what? - like why does my method not also work?) (I was trying to find speed using v = (2*pi*r)/T and then pluging v in ac = v^2 /r )
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by s3a View Post
    Thanks for telling me how to get (a) right but why is my method wrong?(Bad logic or bad formula or what? - like why does my method not also work?) (I was trying to find speed using v = (2*pi*r)/T and then pluging v in ac = v^2 /r )
    I am tempted to say: How would I know, in the brief look I had it looked confused and I could not be bothered to try and work out what you were trying to do?

    It should work so I presume your arithmetic is in error.




    CB
    Attached Thumbnails Attached Thumbnails Uniform Circular Motion Problem-gash.jpg  
    Last edited by CaptainBlack; February 28th 2010 at 11:42 AM.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Is this Right? Circular Motion Problem
    Posted in the Advanced Applied Math Forum
    Replies: 1
    Last Post: January 4th 2009, 05:20 AM
  2. Circular Motion Problem
    Posted in the Math Topics Forum
    Replies: 2
    Last Post: October 30th 2008, 05:03 AM
  3. uniform circular motion
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: September 28th 2008, 12:20 PM
  4. Uniform Circular Motion
    Posted in the Calculus Forum
    Replies: 7
    Last Post: September 18th 2008, 02:30 PM
  5. Circular Motion Problem
    Posted in the Advanced Applied Math Forum
    Replies: 1
    Last Post: April 14th 2008, 04:08 AM

Search Tags


/mathhelpforum @mathhelpforum