Vehicle Dynamics Flashcards
A large percentage of departmental accidents occur _____
while the vehicle is being operated at low speeds.
Many accidents involve _____
fixed or stationary objects.
Rear Wheel Cheat: What is happening?
The path of the rear tires may be as much as 36 inches closer to the inside of the turning radius than the front tires.
Rear Wheel Cheat: Corrections (2)
(1) Swing wide enough to allow space for the rear of the vehicle to clear the hazard.
(2) Proceed in a straight line until the rear axle is aligned with the hazard. The turn can then be accomplished without any danger of the rear of the vehicle contacting the hazard.
When operating in confined areas, a driver can best accomplish accurate vehicle placement by guiding primarily on the _____ side of the vehicle and leaving the maximum amount of available space on the _____ side of the vehicle.
left, right
Front-End Swing: What is happening?
The front of the vehicle will swing out to the left as much as 4 feet.
Front-End Swing: What are the complications?
(1) Limited vision to the rear
(2) Vehicle steering is now reversed
(3) Controls are awkward to reach
Front-End Swing: Corrections (2)
(1) Position the vehicle as closely as possible in the direction the vehicle is to be turned.
(2) Turn the vehicle no more than necessary to accomplish the maneuver.
Backing: Body Position
Upper body turned toward the right, the right arm on the seat back and the left hand positioned toward the top of the steering wheel. This will allow the driver maximum vision through the rear window.
Backing: Utilizing left mirror/window/door only,
should not be attempted as a driver will not be able to see hazards toward the right rear of the vehicle.
Backing: Speed
As speed is increased in reverse, steering smoothness becomes more important and, as many have experienced, small movements of the steering wheel may result in violent weight transfer and erratic steering control.
As speed is increased in reverse, steering smoothness becomes more important and small movements of the steering wheel may result in _____
violent weight transfer and erratic steering control.
Backing: Limited or obstructed viability to the rear.
Utilize side rear view mirrors as well as a back-up camera if equipped. Drivers need to confirm the blind spot directly behind the vehicle is clear prior to beginning any backing maneuvers.
Brake Failure is _____
a mechanical malfunction in the braking system.
Brake Failure (Re)Actions: Gearing
Downshifting to the lowest gear available may reduce speed enough to steer around a hazard.
Downshifting to the lowest gear available may _____
reduce speed enough to steer around a hazard.
Brake Failure (Re)Actions: Steering
It may be best to concentrate on steering and the power of the engine to get out of the situation.
Brake Failure (Re)Actions: Forcible stop
If no open escape route is available, the last and most undesirable alternative may be to lessen the force of a collision by attempting a sideswipe collision with parked vehicles or an embankment.
Brake Failure (Re)Actions: Decision making
A driver experiencing total brake failure must remember, above all, that they still retain steering and throttle control of the vehicle. Panic and indecision can result in the driver losing complete control of the vehicle when resolute action is most needed.
A driver experiencing total brake failure must remember, above all, that they still retain _____
steering and throttle control of the vehicle.
Brakes, when overused and consequently overheated, will begin to lose their braking efficiency. This is termed _____
“brake fade.”
When brakes are _____ , will begin to lose _____
overused and overheated, their braking efficiency.
Brake fade usually occurs on _____ or in a _____
steep downgrades, pursuit.
Brake fade usually occurs due to _____
frequent, hard brake applications.
Kinetic energy must be converted to _____ in order to slow or stop a vehicle. This _____ must be _____ by the braking system as a vehicle stops.
heat, heat, dissipated
Slowing the vehicle from _____ mph to 70 mph as would be required in slowing from 70 mph to a complete stop.
90
A driver encountering brake fade should attempt to
slow the vehicle by other means, as an effort to _____
allow the brakes to cool.
The acronym ABS is _____
Anti-lock Brake System
Anti-lock brake system (ABS) is to _____
prevent wheel lock-up under heavy braking conditions.
Anti-lock brake system (ABS) is desirable because _____
a vehicle which is stopped without locking the wheels will allow the driver to maintain directional stability and some steering capability (rolling friction).
Anti-lock brake system (ABS) does not provide a benefit when hydroplaning because _____
the tires ride on a film of water resulting in the tire leaving the road surface, rendering the vehicle virtually uncontrollable.
Anti-lock brake system (ABS) is not intended to _____, but to _____
stop a vehicle in a shorter distance,
maintain directional stability and some steering capability (rolling friction).
If a wheel sensor detects a wheel is about to lock up, _____, providing maximum braking efficiency without wheel lock-up.
the microprocessor rapidly modulates hydraulic pressure to that brake, either left front, right front, or both rear brakes
During Anti-lock brake system (ABS) operation, the driver will experience _____
a pulsating sensation through the brake pedal.
Do not release brake pressure when the Anti-lock brake system (ABS) is operating, but maintain _____
firm, steady braking pressure until the maneuver is complete.
The acronym ESC is _____
Electronic Stability Control
Electronic stability control (ESC) is computerized technology that _____
improves the safety of a vehicle’s stability by detecting and reducing the loss of traction.
The Electronic stability control (ESC) system compares _____
the driver’s intended direction of travel to the vehicle’s actual direction.
The Electronic stability control (ESC) intervenes only when
it detects a probable loss of steering control, when the vehicle is not going where the driver is steering.
Electronic stability control (ESC) monitors three sensors:
(1) Wheel speed
(2) Steering angle (driver input)
(3) Rotation rate (rotation around center axis, “yaw”)
The Electronic stability control (ESC) does not improve a vehicle’s cornering performance; instead, it _____
helps to minimize the loss of control.
The Electronic stability control (ESC) attempts to _____
prevent loss of control due to oversteer and understeer “Slip Angle” conditions.
Electronic stability control (ESC) can reduce _____
engine power until control is regained.
If the Electronic stability control (ESC) warning light flashes and the ESC system is engaged, the driver should _____
utilize less throttle and steer in the intended direction of travel, and maintain steering input for the intended path through the turn while easing off the throttle.
Attempting to countersteer while Electronic stability control (ESC) is active can act to _____
defeat the effectiveness of Electronic stability control (ESC).
ven Electronic stability control (ESC) can never _____
overcome careless driving actions.
Proper use of _____ will avoid the activation of ESC.
good performance driving techniques
Left-foot braking should not be practiced.
True - False
True
Wet Brakes may be dried out by _____
lightly pressing the brake pedal.
Acceleration skids involve the _____
(rear) drive wheels.
In a turn, acceleration skids will usually progress to _____ with rear-wheel drive vehicles, or _____ with front- or all-wheel drive vehicles.
oversteer, understeer “Slip Angle”
Acceleration Skids results in a (faster or slower) start than controlled acceleration.
slower
Two types of braking skids:
(1) Locked-Wheel
(2) Impending
Locked-wheel skids are undesirable because, _____
the driver relinquishes all directional control of the
vehicle.
If all four wheels lock, _____
the vehicle will have a tendency to rotate.
An impending skid allows the driver _____
to retain directional control of
the vehicle because the wheels are
still rolling.
An impending skid on clean pavement will leave _____
traces of rubber, but not solid black skids.
Most automobiles are designed so the vehicle wants to _____
go in a straight line.
_____ force, the force that tends to pull the vehicle toward the outside of a turn, may overcome the driver’s input of _____ force necessary to allow the vehicle to negotiate a turn.
Centrifugal, centripetal
Understeer should not be confused with the principle of _____. In an understeer “Slip Angle” condition, the front tires are skidding sideways even though they are still rolling.
rolling friction
In an understeer “Slip Angle” condition, the front tires are _____
skidding sideways even though they are still rolling.
Understeer “Slip Angle” is caused by three things:
(1) Entering a turn to fast
(2) Accelerating to early in a curve
(3) Abrupt steering input while cornering
Entering a curve at an excessive speed causes understeer “Slip Angle” by _____
overcoming the cohesion between the tires and the roadway.
Accelerating to early in a curve causes understeer “Slip Angle” by _____
transferring weight to the rear-end, lightening the steering wheels. Additionally there is a straight-ahead push from the rear drive wheels.
Abrupt steering input in a curve causes understeer “Slip Angle” by _____
causing a loss of traction.
“Slip Angle” is the difference between _____
the angle the wheel is turned and the angle of the tire tread contacting the roadway.
A common example of understeer “Slip Angle” is shown with a driver attempting a _____
U-turn.
Oversteer means simply that _____
the rear of the vehicle slides to the outside of a curve as the front of the vehicle tightens its turning radius.
Oversteer can be caused by:
(1) Braking into a turn
(2) Abrupt steering input
(3) Sudden changes in throttle (accelerate or release accelerator)
(4) Cohesion due to environmental conditions
(5) Traction during understeer “Slip Angle”
When in an understeer “Slip Angle” condition, an oversteer condition can occur because _____
traction will be regained by the front tires which are now turned sharper than necessary to negotiate the radius of the turn. At this point, the vehicle turns abruptly toward the inside of the curve which causes the rear tires to exceed cohesion and the vehicle almost instantly attains a condition of oversteer.
Four-wheel drift describes that condition when a cornering vehicle is _____
beyond the limits of cohesion and in a balanced understeer/oversteer attitude.
Four-wheel drift is dangerous because _____
there is no margin of safety. A driver encountering foreign material, obstacles in the roadway, or any unexpected traffic hazard would be virtually helpless to avoid a collision
_____ weight transfer is accomplished when accelerating or decelerating.
Longitudinal
Longitudinal weight transfer is accomplished when _____
accelerating or decelerating.
Longitudinal weight transfer during braking may cause _____
oversteer if too much forward weight transfer is gained at curve entry, lightening the rear end.
_____ weight transfer is incurred when a vehicle is turned right or left from its course of travel.
Lateral
Lateral weight transfer is incurred when a vehicle is _____
turned right or left from its course of travel.
Lateral weight transfer causes the suspension to be
compressed on one side and stretched on the opposite side.
Lateral weight transfer stores potential energy in the suspension which can
induce a violent lateral weight transfer. if immediately turned in the opposite direction.
The only effective way to minimize and control lateral weight transfer is to _____
have smoothness of operation in steering, braking, and throttle.
Performance driving techniques utilize:
control of steering, throttle, braking and closure rate judgement.
A turn should always be entered at _____
a speed that is less than maximum.
All braking should be _____
done prior to entering a turn.
In selecting the proper position for a turn, a driver should _____
attempt to attain a high entry and drive the vehicle through on the line of least resistance or minimum stress to the vehicle.
While attempting to establish proper position or line through a curve, the driver must _____
laterally scan the curve while approaching.
The path of travel through a curve should bring the vehicle from the high side to the _____
apex or low side of the turn just prior to that time when the vehicle is pointed out of the turn.
If a curve is properly negotiated, the driver could, if
necessary, _____
exit the turn on either side of the roadway.
Two key points to safe cornering are _____
entry speed and proper entry position
Shuffle steering requires the use of _____
balanced-hand position, most common are a “10 and 2,” “9 and 3,” or “8 and 4” position.
_____ steering minimizes the potential for air bag injury from your arms in the event of a collision.
Shuffle
The left leg _____ when negotiating sharp curves.
can improve stability and assist to “lock” the driver behind the wheel
“Siren syndrome” is caused by
excitement of the moment, adversely affecting your ability to concentrate and safely operate a vehicle under emergency response or pursuit driving conditions.
The effect of siren syndrome includes _____
increased adrenaline flow, tunnel vision, and loss of speed reference.
To combat the effects of siren syndrome, _____
make a conscious effort to raise the visual horizon, remain calm, take deep breaths, drive with deliberate caution, and glance at the speedometer periodically.
If you cannot see ahead around the curve,
reduce the vehicle speed.
Looking far enough ahead (high visual horizon) is _____
the single most important factor in attaining smoothness in the control of the vehicle.
