Anonymous
Anonymous asked in Science & MathematicsPhysics · 1 month ago

a car is moving 15 m\s north needs to stop in 100 m. what acceleration is required? A. +2m/s2 B. -15 m/s2 C.-1m/s2 D. 0 m/s2?

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  • NCS
    Lv 7
    1 month ago

    There are a couple of methods.

    by kinematics:

    v² = u² + 2ad

    (0m/s)² = (15m/s)² + 2 * a * 100m

    a = -225m²/s² / 200m ≈ -1 m/s² ◄ C

    by work/energy:

    KE becomes friction work:

    KE + W = 0

    ½mv² + m*a*d = 0

    mass m cancels

    a = -v² / 2d = -(15m/s)² / 2*100m ≈ -1 m/s² ◄ C

  • oubaas
    Lv 7
    1 month ago

    (0-Vi^2) = 2*a*d

    a = -(Vi^2)/2d = -225/200 = -1.125 m/sec^2 (-1.1 with just two sign. digits)

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