This question is typical on some driver’s license exams:?

A car moving at 44 km/h skids

12 m with locked brakes.

How far will the car skid with locked brakes

at 110 km/h? Assume that energy loss is due

only to sliding friction.

Answer in units of m

3 Answers

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  • 4 weeks ago
    Favorite Answer

    The constant is the deceleration of the car. I suggest that you use the following equation to calculate the acceleration.

    vf^2 = vi^2 + 2 * a * d

    The first step is to convert the velocity from km/h to m/s.

    1 km = 1,000 m

    1 h = 3,600 s

    1km/h = 1000/3600 = 5/18

    v1 = 44 * 5/18 =220/18

    v2 = 110 * 5/18 = 550/18

    0 = (220)^2 = 2 * a * 12

    a = -(220/18)^2 ÷ 24

    The acceleration is approximately -6.22 m/s^2

    0 = (550/18)^2 + 2 * -[(220/18)^2 ÷ 24] * d

    d = (550/18)^2 ÷ -[(220/18)^2] * 2 = 75 meters

    Now let me show you a much easier way to solve this problem. According to the following equation, the distance the skids is directly proportional to the square of the initial velocity.

    vf^2 = vi^2 + 2 * a * d

    110^2 ÷ 44^2 = 6.25

    Let’s multiply the initial distance by this number.

    d2 = 12 * 6.25 = 75 meters

    This makes this problem easy to solve!

  • JetDoc
    Lv 7
    4 weeks ago

    No. little Snowflake. This "question" is NOT typical of drivers license exams. It's more like a homework question from a physics class.

  • 4 weeks ago

    The amount of energy, and therefor the distance of the skid, is proportional to the square of the speed.  So:

    12 m * (110/44)² = 75 m

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