Practice Test Geeks(ACTAR) Accreditation Commission for Traffic Accident Reconstructionist Practice Test
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Vehicle 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 Vehicle Dynamics flashcards as text

  1. What is the 'center of gravity height' effect on rollover threshold?

    Answer: Higher CG lowers the rollover threshold, making rollover more likely at lower lateral accelerations

    A higher center of gravity increases the overturning moment relative to the stabilizing moment, reducing the lateral acceleration needed to initiate rollover.

  2. What is the significance of the 'static stability factor' (SSF) in rollover analysis?

    Answer: SSF = track width / (2 × CG height); higher SSF means greater rollover resistance

    The Static Stability Factor equals half the track width divided by the CG height; a higher ratio indicates the vehicle can sustain greater lateral acceleration before rolling over.

  3. How does 'load transfer ratio' (LTR) differ from static stability factor in rollover analysis?

    Answer: LTR is a dynamic measure using actual wheel loads during a maneuver, while SSF is a static geometric ratio

    LTR uses the actual difference in wheel normal forces during a dynamic event (LTR = (F_right - F_left)/F_total), making it a real-time dynamic measure versus SSF's static geometric estimate.

  4. What is 'dwell time' in steering input analysis and why is it relevant to crash reconstruction?

    Answer: The duration a steering wheel is held at a particular angle before being returned or reversed

    Dwell time is how long a driver maintains a steering angle, which affects the magnitude of lateral displacement achieved and can indicate intentional versus panic steering.

  5. A vehicle with a wheelbase of 110 inches has its CG located 48 inches behind the front axle. What percentage of vehicle weight is on the front axle (static)?

    Answer: 56.4%

    Front axle load % = (distance from CG to rear axle / wheelbase) × 100 = (110−48)/110 × 100 = 62/110 × 100 ≈ 56.4%.

  6. What phenomenon causes a vehicle's natural tendency to return to straight-line travel after a steering disturbance?

    Answer: Caster angle and pneumatic trail providing self-aligning torque

    Positive caster angle places the steering axis ahead of the tire contact patch, and pneumatic trail creates a self-aligning torque that naturally returns the wheels to straight-ahead.

  7. In the context of vehicle dynamics, what is 'jounce' and 'rebound'?

    Answer: Jounce is suspension compression (wheel moving up); rebound is suspension extension (wheel moving down)

    Jounce (bump) describes the suspension compressing as the wheel moves upward toward the body, while rebound describes the suspension extending as the wheel moves downward.