ACTAR Mathematical & Physical Principles of Reconstruction 2

Question 1

A vehicle skids to a stop leaving 120 feet of skid marks on a road with a drag factor of 0.75. Using the skid-to-stop formula, what was the approximate minimum speed?

Accepted Answer

51.5 mph

Answer

Using S = √(30 × d × f) = √(30 × 120 × 0.75) = √2700 ≈ 51.96 mph, which rounds to approximately 51.5 mph.

Question 2

In projectile motion analysis of a vehicle that launches off a cliff, which two components of initial velocity are treated as independent?

Accepted Answer

Horizontal and vertical

Answer

Projectile motion treats horizontal velocity as constant (no air resistance assumed) and vertical velocity as independently accelerated by gravity.

Question 3

What is the centripetal acceleration of a vehicle traveling at 60 ft/s around a curve with a radius of 300 feet?

Accepted Answer

12.0 ft/s²

Answer

Centripetal acceleration a = v²/r = (60)²/300 = 3600/300 = 12.0 ft/s².

Question 4

Conservation of momentum in a two-vehicle collision is valid only when:

Accepted Answer

No external forces act on the system during impact

Answer

Conservation of momentum applies when the net external force on the system is zero, meaning no significant external forces act during the brief impact interval.

Question 5

A vehicle with a weight of 3,200 lbs has a coefficient of friction of 0.72 with the road. What is the maximum frictional braking force available?

Accepted Answer

2,304 lbs

Answer

Frictional force = weight × coefficient of friction = 3,200 × 0.72 = 2,304 lbs.

(ACTAR) Accreditation Commission for Traffic Accident Reconstructionist Practice Test

(ACTAR) Accreditation Commission for Traffic Accident Reconstructionist Practice Test

ACTAR Mathematical & Physical Principles of Reconstruction 2