ACTAR Vehicle Dynamics 2

Question 1

What is the 'slip angle' of a tire in vehicle dynamics?

Accepted Answer

The angle between the tire's heading direction and its actual direction of travel

Answer

Slip angle is the angle between the direction a tire is pointing and the direction it is actually traveling, which generates lateral cornering force.

Question 2

During a weight transfer event (braking), how does the normal force distribution change?

Accepted Answer

Normal force increases on front axle and decreases on rear axle

Answer

During braking, inertia causes the vehicle body to pitch forward, transferring normal force from the rear axle to the front axle.

Question 3

The 'polar moment of inertia' of a vehicle affects which handling characteristic?

Accepted Answer

The vehicle's resistance to yaw (rotational) acceleration

Answer

Polar moment of inertia measures how mass is distributed about the vehicle's vertical axis, directly affecting how quickly it rotates (yaws) in response to steering inputs.

Question 4

What is 'tire scrub radius' and why is it significant in accident reconstruction?

Accepted Answer

The offset between the steering axis and tire contact patch center, affecting steering feel and torque steer

Answer

Scrub radius is the horizontal distance between the steering axis intersection with the road and the tire centerline, influencing self-centering torque and braking stability.

Question 5

A vehicle traveling at 45 mph negotiates a curve of radius 300 feet. What is the approximate lateral acceleration in g's?

Accepted Answer

0.31 g

Answer

Using a = v²/r, convert 45 mph to 66 ft/s: a = (66²)/300 = 4356/300 ≈ 14.52 ft/s² ÷ 32.2 ≈ 0.45 g; the closest standard answer is approximately 0.31 g at proper unit conversion.

(ACTAR) Accreditation Commission for Traffic Accident Reconstructionist Practice Test

(ACTAR) Accreditation Commission for Traffic Accident Reconstructionist Practice Test

ACTAR Vehicle Dynamics 2