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Homework Help: Please Help Vector Forces in 2D

  1. Sep 15, 2005 #1

    wr1015

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    A shopper pushes a 7.3 kg shopping cart up a 13° incline, as shown in Figure 5-21. Find the horizontal force, F, needed to give the cart an acceleration of 1.63 m/s2.

    ok, here is the formula to find horizontal force:

    sum Fx= F1x +F2x = F1 + F2cos(theta), which also =mAx

    if there are no forces given, how do i calculate F2cos(13degrees) and F2sin(13degrees)???
     

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    Last edited: Sep 15, 2005
    wr1015, Sep 15, 2005
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  3. Sep 15, 2005 #2

    Tom Mattson

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    You would leave your answer in terms of the given symbols.
     
    Tom Mattson, Sep 15, 2005
  4. Sep 15, 2005 #3

    wr1015

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    my answer is supposed to be in Newtons, but my question is how to calculate acceleration in the x direction??
     
    wr1015, Sep 15, 2005
  5. Sep 15, 2005 #4

    Tom Mattson

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    Duh, I didn't read the problem statement very carefully. :tongue: Yes, you will get an answer in Newtons.

    Instead of resorting to a canned formula, you should draw a free body diagram and write down equations for the sum of the forces in the x and y directions. You've got the normal force, the applied force, and gravity.
     
    Tom Mattson, Sep 15, 2005
  6. Sep 15, 2005 #5

    wr1015

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    ok so normal force = mass of cart x acceleration of gravity: F=(7.3kg)(9.81 m/s2) = 71.613N, whats the applied force?
     
    wr1015, Sep 15, 2005
  7. Sep 15, 2005 #6

    Tom Mattson

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    No, because the cart is on an incline.

    That's the unknown.
     
    Tom Mattson, Sep 15, 2005
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