Practice Test Geeks(ACTAR) Accreditation Commission for Traffic Accident Reconstructionist Practice Test
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Crash Dynamics Flashcards

7 cards from real ACTAR practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Crash Dynamics flashcards as text

  1. Which physical principle explains why an unrestrained occupant continues moving forward at the vehicle's pre-crash speed when the vehicle suddenly decelerates?

    Answer: Newton's First Law (inertia)

    Newton's First Law states that a body in motion continues at constant velocity unless acted upon by a net force; an unrestrained occupant lacks the restraining force the seatbelt would provide.

  2. When analyzing a low-speed rear-end collision, which factor most significantly affects the magnitude of delta-V experienced by the struck vehicle?

    Answer: Mass ratio between the striking and struck vehicles

    The mass ratio between the striking and struck vehicles directly determines how momentum is partitioned, making it the dominant factor in delta-V for the struck vehicle.

  3. In crash dynamics, 'restitution phase' refers to:

    Answer: The period during which vehicles spring apart after reaching maximum crush

    The restitution phase follows maximum engagement, during which stored elastic energy releases and the vehicles begin to separate.

  4. A vehicle traveling at 30 mph skids to a stop on dry asphalt with a drag factor of 0.75. Approximately how far does it skid before stopping?

    Answer: 80 ft

    Using the skid formula d = S²/(30f): d = 30²/(30 × 0.75) = 900/22.5 = 40 ft.

  5. Which of the following best describes 'impulse' in the context of crash dynamics?

    Answer: The product of force and the time over which it acts

    Impulse equals force multiplied by the duration of its application (J = F×Δt), and by the impulse-momentum theorem, it equals the change in momentum.

  6. During a rollover event, which energy component must be accounted for in addition to translational kinetic energy?

    Answer: Rotational kinetic energy

    A rolling vehicle possesses rotational kinetic energy (½Iω²) in addition to translational kinetic energy (½mv²), and both must be considered in a full energy analysis.

  7. In pedestrian impact reconstruction, the 'wrap projection' distance is used to estimate the vehicle's speed because it reflects:

    Answer: The horizontal distance the pedestrian traveled through the air after being struck by the hood

    Wrap projection distance is the horizontal distance a pedestrian travels as a projectile after being struck and launched over the vehicle hood, correlated to impact speed through validated formulas.