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Homework Help: Forces on an inclined plane

  1. Mar 22, 2012 #1
    A Black Garden Ant is seen dragging a caterpillar with mass = 1.5g = .0015 KG
    the ant manages to accelerate the caterpillar at 1mms^-2

    Assume that friction between the caterpillar and the ground can be ignored.

    (a) What force has the ant applied to cause this acceleration?

    (b) The ant bites the caterpillar near to the ground and pulls it an angle of 30° to the horizontal.
    What total force does it have to apply to move the caterpillar with the same horizontal acceleration?

    (c) What is the normal force acting on the caterpillar whilst being pulled by the ant at 30°

    have missed out on a week of classes due to being sick and have no idea what to do here.

    EDIT: i think this is right now, but not sure


    F = .0015kg x .001m/s
    F = 0.0000015N

    let x = horizantal
    let y = vertical
    let z = hypotenenuse

    cos 30 = x/z
    f= x/cos 30
    f = 1.732 x 10^-6

    c) w = .015N
    normal force(N):
    N = w - y
    N = .014999
    Last edited: Mar 22, 2012
  2. jcsd
  3. Mar 22, 2012 #2
    Your drawing appears correct.

    a) Your calculated force is wrong, you forgot to convert g to kg.
    b) You need to find the force on the diagonal, use the Pythagorean theorem.
    c) Normal force on a slope is calculated as mgcos[itex]\theta[/itex]
  4. Mar 22, 2012 #3


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    Welcome to PF!

    Hi Koborl! Welcome to PF! :smile:
    hmm … you obviously missed all the information about black garden ants :redface:

    nooo, your diagram is completely wrong, the ground is horizontal, the caterpillar is horizontal, but the ant is dragging it with a force at 30° to the horizontal (as if it was pulling it with a string at that angle)

    in future, please go to your nearest black garden and study the ants there before attempting questions like this! :biggrin:

    however does he expect to pass his physics exams without minoring in ant studies? :rolleyes:
  5. Mar 22, 2012 #4
    Oh wow, totally didn't see the block ON the hill, thought he was pulling on it xD. Thanks tim.
  6. Mar 22, 2012 #5
    1.[itex]Force(Kg \frac{m}{sec^2} or \frac {ML}{T^2})=ma \ N[/itex]

    2. On inclined plane 2 forces, and the resultant is ma
    The gravity that pull the caterpillar down, mgSin30°.
    Thus F-mgSin30°=ma

    3. Not sure N on level or inclined plane.

    a) On level plane, the x component of force accelerate the caterpillar.
    The vertical or Y component pulling the object up against the weight.
    N=mg -FSin30°
    b) On inclined plane
    [itex]N=mgCos30°-Sin30°(\frac {(ma+mgSin30°)}{Cos30°})[/itex]
    Last edited: Mar 22, 2012
  7. Mar 22, 2012 #6
    N on inclined plane is mgcos[itex]\theta[/itex].
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