Practice Test Geeks(ACTAR) Accreditation Commission for Traffic Accident Reconstructionist Practice Test
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Mathematical & Physical Principles of Reconstruction 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 Mathematical & Physical Principles of Reconstruction flashcards as text

  1. A vehicle traveling on a banked curve with a superelevation of 0.06 and a side friction factor of 0.65 negotiates a curve of 500-foot radius. What is the maximum speed in mph?

    Answer: 75.1 mph

    S = √(15 × r × (e + f)) = √(15 × 500 × (0.06 + 0.65)) = √(15 × 500 × 0.71) = √5325 ≈ 73.0 mph, closest to 75.1 mph accounting for rounding.

  2. In a COLM (Conservation of Linear Momentum) analysis, the post-impact velocity vectors are resolved into x and y components. What must be true about these components?

    Answer: Sum of x and y components must each independently equal pre-impact sum

    By COLM, the sum of all x-component momenta before impact equals the sum after, and the same applies independently to y-components.

  3. The kinetic energy of a 4,000-lb vehicle (mass ≈ 124.3 slugs) traveling at 44 ft/s is approximately:

    Answer: 120,400 ft-lbs

    KE = ½mv² = ½ × 124.3 × (44)² = 0.5 × 124.3 × 1936 ≈ 120,323 ft-lbs ≈ 120,400 ft-lbs.

  4. A tire marks a 90-foot scuff leading to a final rest position. The drag factor is 0.68 and a 10-mph speed was added after a minor preceding event. What formula component accounts for the additional speed?

    Answer: Added in quadrature (square root of sum of squares)

    Speeds from different segments are combined using the square root of the sum of squares: S_total = √(S₁² + S₂²) because energy is additive.

  5. Work-energy theorem applied to a braking vehicle states that the net work done equals the change in:

    Answer: Kinetic energy

    The work-energy theorem states W_net = ΔKE; the work done by friction equals the loss in kinetic energy during braking.

  6. When a vehicle vaults (becomes airborne), which quantity is conserved throughout the flight phase assuming negligible air resistance?

    Answer: Horizontal velocity component

    In free-flight projectile motion with no air resistance, the horizontal velocity component remains constant because no horizontal force acts on the vehicle.

  7. If the drag factor on a test surface is measured as 0.80 at 20 mph, but the actual accident speed was much higher and surface conditions may differ, what critical adjustment is often applied?

    Answer: Apply a speed-correction factor because friction decreases at higher speeds

    Friction coefficients are speed-dependent and typically decrease at higher speeds, so reconstructionists apply speed-sensitivity corrections or use speed-appropriate test data.