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Homework Help: Angular speed

  1. Jun 30, 2010 #1
    1. The problem statement, all variables and given/known data
    A car initially traveling at 33.8 m/s undergoes a constant negative acceleration of magnitude 1.80 m/s2 after its brakes are applied. (a) How many revolutions does each tire make before the car comes to a stop, assuming the car does not skid and the tires have radii of 0.330 m? (b) What is the angular speed of the wheels when the car has traveled half the total distance?

    2. Relevant equations
    v2 = vo2 + 2aΔx

    3. The attempt at a solution
    a. Δx = vo2 /-2a
    Δx = 33.8 m/s 2 / (-2(-1.80 m/s2))
    Δx = 317.3 m

    # rev = 317.3 m / 2π (0.33m)
    # rev = 153.1

    b. v2 = 33.8 m/s2 + 2(-1.80 m/s2)(158.65m)
    v = 23.9 m/s --> ω = 23.9 rad/s
  2. jcsd
  3. Jun 30, 2010 #2
    Everything is fine except the very last step. The tangential velocity of the wheel is related to the angular velocity via vT = rω. The reason you can assume that v = vT is because the wheels do not skid.
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