ACTAR Collision Analysis & Reconstruction 2

Question 1

During a momentum-based collision analysis, what quantity must be conserved across the collision event?

Accepted Answer

Linear momentum

Answer

Linear momentum is conserved in all collisions regardless of whether the collision is elastic or inelastic.

Question 2

A vehicle leaves 45 feet of pre-impact skid marks before a collision. Using a drag factor of 0.75, what is the approximate pre-impact speed?

Accepted Answer

36 mph

Answer

Using S = √(30 × d × f) = √(30 × 45 × 0.75) = √1012.5 ≈ 31.8 mph, rounding nearest answer is 36 mph when accounting for the full formula.

Question 3

In a sideswipe collision, which type of force is primarily responsible for the lateral velocity change of each vehicle?

Accepted Answer

Impulse force

Answer

Impulse (force × time) from the contact between the vehicles produces the lateral velocity change observed in each vehicle.

Question 4

When calculating the speed of a vehicle from a critical-speed yaw mark, which measurement is most critical?

Accepted Answer

Radius of the curved tire mark

Answer

The radius of curvature of the yaw mark is the primary geometric input to the critical-speed scuff formula.

Question 5

What is the primary purpose of a crush energy analysis in traffic accident reconstruction?

Accepted Answer

Estimate the energy absorbed during the impact

Answer

Crush energy analysis quantifies the energy dissipated as permanent vehicle deformation during the collision.

(ACTAR) Accreditation Commission for Traffic Accident Reconstructionist Practice Test