ACTAR Mathematical & Physical Principles of Reconstruction 3

Question 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?

Accepted Answer

75.1 mph

Answer

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.

Question 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?

Accepted Answer

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

Answer

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

Question 3

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

Accepted Answer

120,400 ft-lbs

Answer

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

Question 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?

Accepted Answer

Added in quadrature (square root of sum of squares)

Answer

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

Question 5

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

Accepted Answer

Kinetic energy

Answer

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

(ACTAR) Accreditation Commission for Traffic Accident Reconstructionist Practice Test

(ACTAR) Accreditation Commission for Traffic Accident Reconstructionist Practice Test

ACTAR Mathematical & Physical Principles of Reconstruction 3