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Homework Help: No Physics Tutor Today so I'm Desperate

  1. Nov 10, 2004 #1
    I have been trying to get a hold of my Physics tutor all morning, but he left for the week already the Veteran's Day Holiday cutting the week short and all anyway I only have a couple of questions left and could use some tutoring help on them so here goes:

    1). A 5.0g coin is placed 15cm from the center of a turntable. The coin has static and kinetic coefficients of friction w/ the turntable surface of u_s = 0.80 and u_k = 0.50. The turntable very slowly speeds up to 60 rpm. Does the coin slide off?

    -I know that the coin does not slide off but I am unsure of the method in which I came about that answer. Anyone have any ideas of how to determine that the coin does not slide off?

    2). In an amusement park ride called the roundup passengers stand inside a 16-m-diameter rotating ring. After the ring has acquired sufficient speed it tilts into a vertical plane. Suppose the ring rotates once every 4.5sec. If a rider's mass in 55kg w/ how much force does the ring push on her at the top of the ride and at the bottom of the ride?

    3). A soccer ball and a bowling ball roll across a hard floor and collide head on. Identify all action/reaction pairs during the time that the balls are in contact.

    I know that these are maybe not the hardest questions in the world, but I am used to going through these probs step by step with classmates or my tutor. All I really need is a starting point and then I am usually good to go. So please if you have any useful information feel free to submit it.
  2. jcsd
  3. Nov 10, 2004 #2
    d = 16m, so r = 8m...
    t = 4.5s
    m = 55kg, and F = ?
    F_c = m(v^2/r), and we know that v will be found by [2(Pi)(r)]/t
    And solve..
  4. Nov 10, 2004 #3
    Tutorless in Ellensburg, WA

    Maybe something is wrong with my math, but I keep coming up with 319N at the top of the ride and 1400 at the bottom. Anyone else confirm this or tell me somethinig different? I'm all ears (or is it eyes?).
  5. Nov 10, 2004 #4

    Doc Al

    User Avatar

    Staff: Mentor

    Show your work and we can check it out.
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