Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Physics problems with Newton's Law

  1. Sep 21, 2004 #1
    These problems are really giving me fits, I would really appreciate some help.

    A 12200 kg sailboat experiences an eastward
    force of 27400 N due to tide pushing its hull
    while the wind pushes the sails with a force of
    56200 N directed toward the northwest (45±
    westward of North or 45± northward ofWest).
    What is the magnitude of the resultant ac-
    celeration of the sailboat?



    I'm using Fr= square root of (Frx squared)+(Fry squared) but I'm still not getting it right. I'm thinking that maybe I drew the free body diagram wrong. Any help?

    Now for this one

    The distance between two telephone poles is
    32 m. When a 1:15 kg bird lands on the
    telephone wire midway between the poles, the
    wire sags 0:182 m.
    The acceleration of gravity is 9:8 m=s2 :
    How much tension in the wire does the
    bird produce? Ignore the weight of the wire.

    So far I've drawn the diagram and got a hypotenuse of 16.001 m, but I'm unsure how to finish the problem.

    Any help would be much appreciated.
     
  2. jcsd
  3. Sep 22, 2004 #2
    1. Find the magnitude using the cosine law.
    2. use F=ma to find the magnitude of a.
    It is easier to use the unit vector i and j. but i am afraid you haven't learnt that yet. so we will approach it geometrically.
     

    Attached Files:

  4. Sep 22, 2004 #3
    First problem (sail boat)

    check the attachment

    Fx = F(east) - F(northwest)Xcos45 = -12339 N
    Fy = F(northwest)Xsin45 = 39739 N
    Fnet = Squareroot of (Fx^2 + Fy^2)
    then, Fnet = ma
    a = Fnet/mass = 3.4 m/s
     

    Attached Files:

  5. Sep 22, 2004 #4
    2nd problem

    ok the hyp that you got is good.
    a^2 + b^2 = c^2
    a= 16
    b = .182
    c = 16.001 using the formula. Good you got until this point.

    2nd step= get the angle theta. (see diagram)

    90-tan (16/.182) = theta


    step 3 = Get the tension by adding the Forces on the y axes. See diagram
     

    Attached Files:

  6. Sep 22, 2004 #5
    Free body diagram : Attached file.
     

    Attached Files:

  7. Sep 22, 2004 #6
    of course, I didn't draw the other tension on the other side because is understood.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Physics problems with Newton's Law
Loading...