Results 1 to 4 of 4

Math Help - Finding the magnitude of forces acting on a body

  1. #1
    Member
    Joined
    Jan 2009
    From
    Ontario Canada
    Posts
    219

    Question Finding the magnitude of forces acting on a body

    Two forces Fa and Fb are applied to an object whose mass is 8.0kg. Fa is the larger force. When both forces point due east, the objects acce. has a magnitude of .50m/s.s. However, when Fa points due east and Fb points due west, the acc is 0.40m/s.s. Find a) magnitude of Fa and b) the magnitude of Fb.

    I tried it and came up with a) as 4N, but the answer is 3.6N. I did m x a=F
    I don't have a clue how to get 0.40 N for the answer of b).

    Can someone help me get started on this please.

    I looked thru the little notes I have, which do not help and going thru my book, has nothing like this.
    Thanks.
    Joanne
    Follow Math Help Forum on Facebook and Google+

  2. #2
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by bradycat View Post
    Two forces Fa and Fb are applied to an object whose mass is 8.0kg. Fa is the larger force. When both forces point due east, the objects acce. has a magnitude of .50m/s.s. However, when Fa points due east and Fb points due west, the acc is 0.40m/s.s. Find a) magnitude of Fa and b) the magnitude of Fb.

    I tried it and came up with a) as 4N, but the answer is 3.6N. I did m x a=F
    I don't have a clue how to get 0.40 N for the answer of b).

    Can someone help me get started on this please.

    I looked thru the little notes I have, which do not help and going thru my book, has nothing like this.
    Thanks.
    Joanne
    Yes, use \displaystyle F = ma

    Now, we take east to be the positive direction and west to be the negative.

    When both forces point east, the force is the sum of the forces, this is equal to mass times acceleration. That is,

    \displaystyle F_a + F_b = 8 (0.5)

    Similarly, when \displaystyle F_b points in the negative direction, we get

    \displaystyle F_a - F_b = 8(0.4)

    Now you have a system of two equations with two unknows ( \displaystyle F_a and \displaystyle F_b), solve this system to get your answer.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member
    Joined
    Jan 2009
    From
    Ontario Canada
    Posts
    219
    OMG, I did not that it included equation. The teacher never said this would be used. oh man.
    I got it now.
    It's substitution for one of the letters. geeshhhhhhhhhhhh.

    Thanks for the help GOT IT. but would have never thought of this at all tho.
    Does this happen at times in Physics to use this????
    Follow Math Help Forum on Facebook and Google+

  4. #4
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by bradycat View Post
    OMG, I did not that it included equation. The teacher never said this would be used. oh man.
    I got it now.
    It's substitution for one of the letters. geeshhhhhhhhhhhh.
    Really? Are you sure the teacher said that? F = ma is Newton's second law of motion. It is a pretty standard equation to use. I don't think you can go through a basic physics class without using it.

    Thanks for the help GOT IT. but would have never thought of this at all tho.
    Does this happen at times in Physics to use this????
    Hmm, I would suppose it happens all the time, I never took physics. But once you knew what equation to use, it was pretty much a math problem. There's a lot of math in physics, so you can't forget the tricks you learn in math class. Simultaneous equations will come up in many situations. So look out for it.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. finding the magnitude using vector
    Posted in the Algebra Forum
    Replies: 2
    Last Post: April 15th 2010, 03:40 AM
  2. Replies: 6
    Last Post: March 27th 2010, 09:10 AM
  3. Two Forces Acting at a Point
    Posted in the Math Topics Forum
    Replies: 1
    Last Post: November 23rd 2009, 09:57 PM
  4. magnitude forces/resultant/etc.
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: July 30th 2008, 09:41 PM
  5. magnitude of the forces
    Posted in the Advanced Applied Math Forum
    Replies: 2
    Last Post: October 19th 2007, 10:31 AM

Search Tags


/mathhelpforum @mathhelpforum