1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Newton's laws,solving for tension (smthn wrong with my work)?

  1. Oct 5, 2011 #1
    A flat-topped toy cart moves on frictionless wheels, pulled by a rope under tension The mass of the cart is m1. A load of mass m2 rests on top of the cart with the coefficient of static friction u between the cart and the load. The cart is pulled up a ramp that is inclined at an angle theta above the horizontal. The rope is parallel to the ramp. What is the maximum tension T that can be applied without causing to load to slip?

    Okay. I figure this problem is fairly simple right?
    (i) Fx = m2a
    (ii) ff = m2a
    (iii)Fy = 0
    (iv)Fn - m2gcos = 0
    (v) Fn = m2gcos
    Plug v into (ii)
    (vi) um2gcos = m2a
    (vii) a = ugcos
    Now sum forces for the cart
    (vii) T - ff = (m1+m2)a
    Plug in (vi) and (vii)
    T - um2gcos = (m1+m2)(ugcos)
    Here's my problem. The final answer is simply T = (m1+m2)(ugcos). Meaning there's an obvious problem with my work here...

    What's the problem here? I'm so confused!! My teacher suggested "adding m2gsin" to my fx equation, so like m2a + m2gsin? Because I tried that out and it still didn't work. Any help is great help, thanks in advance
     
  2. jcsd
  3. Oct 5, 2011 #2

    Doc Al

    User Avatar

    Staff: Mentor

    What about gravity?
    OK.
    You'll need to fix this since you left out gravity on m2.
    The cart has mass m1, not m1 + m2. (And you forgot about gravity again.)
     
    Last edited: Oct 5, 2011
  4. Oct 5, 2011 #3
    -------

    Right, so does that mean it's m2a + m2gsin, with gravity added? or am I wrong??
     
  5. Oct 5, 2011 #4

    Doc Al

    User Avatar

    Staff: Mentor

    Adding gravity to your m2 equation means adding -m2gsinθ to ƩFx.
     
  6. Oct 5, 2011 #5
    Okay, thanks ^__^
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Newton's laws,solving for tension (smthn wrong with my work)?
Loading...