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Homework Help: Determining static coefficient

  1. May 31, 2007 #1
    1. The problem statement, all variables and given/known data

    An object is on the dash of a car and it slides forward when the driver decelerates from 50 km/h to 0 in 3.0s or less. If the driver decelerates over a longer time it doesn't slide. What is the static coefficient?

    2. Relevant equations

    I'm not sure. I have tried several but I feel like every equation has two unknowns. If I use v=vi + at I can get acceleration. But, then what? I don't have a mass, and it seems that I need that for F=MA, or F=mg, or to figure out Fn.

    3. The attempt at a solution

    I've figured out the Acceleration by using v=vi + at. I can figure out the distance travelled in 3.0s by using x=x1 + Vxt + 0.5gt~2. But without mass, I don't know what else to calculate.
  2. jcsd
  3. May 31, 2007 #2
    Suppose you do know the mass; call it m. What would you have as an answer?
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