ACTAR Crash Dynamics 2

Question 1

During a head-on collision between two vehicles of equal mass and equal speed, what happens to their combined momentum?

Accepted Answer

It equals zero

Answer

When two equal-mass vehicles traveling at equal and opposite speeds collide head-on, their momenta cancel, resulting in a net combined momentum of zero.

Question 2

Which term describes the ratio of the relative separation speed to the relative approach speed of two colliding objects?

Accepted Answer

Coefficient of restitution

Answer

The coefficient of restitution (e) quantifies the elasticity of a collision by comparing post-impact separation speed to pre-impact approach speed.

Question 3

In crash reconstruction, the 'crush stiffness coefficient' (A and B) is used primarily to determine what?

Accepted Answer

Delta-V from crush depth measurements

Answer

The Campbell crush model uses empirically derived stiffness coefficients A and B to relate residual crush depth to the energy absorbed and estimate Delta-V.

Question 4

A vehicle strikes a fixed rigid barrier and comes to a complete stop. If the vehicle's mass is 1,500 kg and its pre-impact speed is 20 m/s, what is its initial kinetic energy?

Accepted Answer

300,000 J

Answer

Kinetic energy = ½mv² = 0.5 × 1,500 × (20)² = 0.5 × 1,500 × 400 = 300,000 J.

Question 5

What is the primary reason vehicle roof crush is analyzed separately from frontal/side crush in ACTAR reconstructions?

Accepted Answer

Roof crush involves different energy absorption mechanics and occupant space intrusion concerns

Answer

Roof crush analysis focuses on structural intrusion affecting occupant survival space, governed by different stiffness characteristics than frontal or side impacts.

(ACTAR) Accreditation Commission for Traffic Accident Reconstructionist Practice Test

(ACTAR) Accreditation Commission for Traffic Accident Reconstructionist Practice Test

ACTAR Crash Dynamics 2