Collision Analysis & Reconstruction Flashcards

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

Answer: Linear momentum

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

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?

Answer: 36 mph

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.

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

Answer: Impulse force

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

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

Answer: Radius of the curved tire mark

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

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

Answer: Estimate the energy absorbed during the impact

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

In a pedestrian-vehicle collision, which phase describes the pedestrian's initial contact with the vehicle hood?

Answer: Primary contact phase

The primary contact phase is the initial moment when the vehicle strikes the pedestrian, before the pedestrian is thrown onto the hood.

Which formula correctly relates time, distance, and constant acceleration for a vehicle starting from rest?

Answer: d = ½ × a × t²

For a vehicle starting from rest under constant acceleration, d = ½ × a × t² is the correct kinematic equation.