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Homework Help: Force and Newton law of Motion

  1. Sep 23, 2006 #1
    hi there i have a question in which i can't get the answer i will show my work on what i did, if anybody can help , that would help alot .

    here is the question:

    only two forces act on an object (mass= 3kg)

    a=60N is at 45 degrees above the horizon
    y= ?
    find the magnitude and direction (relative to the x-axis) of the acceleration of the object?

    i can use (a=60N)sin(45)= 42.42degrees, but where do i go from here, or whats the next step, i did try squaring y+x under the square root, but thats not the magnitude, because the answer in teh back of the book is different.

    any help is welcome thanks:smile:
  2. jcsd
  3. Sep 23, 2006 #2
    Ok first of all the 42.42 value wont be in degrees, it will be in newtons. Secondly, draw a diagram, it always helps.

    In order to help you more i need to know which direction the x force is in. so draw up what you think is happeneing and then attach it.

    In essence you are just resolving vector components of a force, and need to draw a few triangles and stuff to find the resultant
  4. Sep 24, 2006 #3


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    Homework Helper

    Newton's second law can be applied in component form:

    [tex]\Sigma F_x = ma_x[/tex]

    that is

    [tex]a_x = \frac{\Sigma F_x}{m}[/tex]

    so to get the acceleration in the x-direction you need to add the force components acting on the object in the x-direction and divide that by its mass.
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