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TARSC > TAR I Chapter Quizes > Flashcards

TAR I Chapter Quizes Flashcards

1
Q

What is acceleration?

A

The rate of change in velocity with respect to time.

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2
Q

What is the acceleration equation?

A

Acceleration = change in velocity / change in time or delta v / delta t

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3
Q

What is constant acceleration?

A

A type of motion in which the velocity of an object changes an equal amount in equal time periods

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4
Q

How many basic values are considered in the kinematic equation?

A 
Five:
Velocity - initial
Velocity - final
Acceleration 
Distance
Time
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5
Q

The kinematic equations are equations for motion with __________ ____________

A

Constant Acceleration

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6
Q

What will cause a change in acceleration while a vehicle is in full braking?

A

A change in the surface

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7
Q

Do kinematic equations apply to a moving vehicle that is not braking or accelerating?

A

No, kinematic equations are only used when there is constant acceleration (either positive or negative).

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8
Q

If a vehicle passes over multiple surfaces, the initial velocity calculated over the last surface is the _______ _______ used to calculate the initial velocity at the prior surface.

A

Final Velocity

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9
Q

True or False: When a vehicle impacts an object and comes to rest, the change in velocity from the impact can be used as the final velocity in calculating velocity over distances prior to the impact

A

True

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10
Q

What are the three circumstances that will cause a Tire Friction Mark (TFM)?

A
  • Extreme Acceleration
  • Extreme Deceleration
  • Extreme Changes of Direction
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11
Q

Describe a tire abrasion with smear

A
  • A smear of tar/asphalt along with abrasions of tire material. They’re long lived and most common on asphalt-concrete surfaces.
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12
Q

What is the primary marking mechanism on a Portland Concrete Cement (PCC) surface?

A

Tire abrasion

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13
Q

TRUE or FALSE: Erasing caused by a locked wheel tire is long lived/long lasting.

A

False

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14
Q

Name the four types of tire friction marks?

A 
S.L.I.P.
Side Skid
Lock Wheel
Impending
Critical Speed Scuff Mark (Yaw Mark)
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15
Q

Define a side skid TFM

A

A mark left by a rotating or non-rotating tire that is sliding or slipping sideways to its direction of travel

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16
Q

Define a locked wheel skid TFM

A

A mark left by a non-rotating tire that is sliding along its direction of travel

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17
Q

Define an Impending skid TFM

A

A mark left by a tire that is rotating slower than the forward velocity of the vehicle

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18
Q

Define a Critical Speed Scuff Mark (Yaw Mark)

A

A mark left by a rotating tire that is slipping sideways and diagonally to its direction of travel

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19
Q

What are characteristics of a CSS mark

A
  • Starting thin and widening
  • Arced
    Striations in a direction at an angle to the direction the vehicle is traveling
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20
Q

When does a CSS mark transition into a side skid?

A
  • When the heading direction of the vehicle exceeds 20 degrees from center mass path of travel of the vehicle (or 1/3 the wheelbase).
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21
Q

The best method for measuring the distance of a straight lined locked wheel tire friction mark used for calculating velocity is:

A: Averaging the TFM
B: Using the longest skid mark

A

B: The longest skid mark

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22
Q

True or False: When a vehicle is rotating during deceleration, the best method for determining the distance the vehicle traveled is the COM movement of the vehicle.

A

TRUE

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23
Q

When might a vehicle be braking and the tire doesn’t leave a TFM?

A
  • All wheels are braking but not enough to lock the wheels

- Some wheels were not braking at all (i.e. 1 brake is disabled or not functioning)

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24
Q

Describe a gouge

A
  • Occurs when strong metal components dig into the road surface.
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25
Q

Describe a chop

A

Deep gouges where chunks of the road surface have been dug out. A good indicator of maximum engagement

26
Q

What are the three types of friction?

A
  • Static
  • Dynamic
  • Rolling
27
Q

Describe Static Friction

A

The friction force when an object is just beginning to slide (i.e. trying to push a fridge)

28
Q

Describe Dynamic Friction

A

Once the object is sliding, the force required for the object to continue sliding is less

29
Q

Describe Rolling Friction

A

The resisting forces when a tire is rolling with no brakind

30
Q

True or False: Coefficient of Friction / Drag Factor is “unit-less”

A

TRUE

31
Q

When is coefficient of friction and drag factor equal?

A

On a flat, level surface and all wheel are locked

32
Q

List the ways (equations) coefficient of friction can be described

A

f = ma/mg

f = Fx/mg

f = a/g

f = Fpull/w

33
Q

What is the difference between coefficient of friction, drag factor, and resultant drag factor

A

Coefficient of Friction is used to quantify the total available force on a roadway surface (the resistance between two surfaces sliding)

Drag Factor is a number used to represent the acceleration or deceleration of a vehicle on a surface (???force required for acceleration or deceleration divided by weight???)

Resultant Drag Factor is an adjusted drag factor for a particular vehicle on a particular surface

34
Q

It is not appropriate to use a drag sled on what type of surfaces?

A

Soft surfaces

- Grass, sand, or gravel

35
Q

Why is there an adjustment in the friction value between passenger tires and commercial truck tires?

A
  • The way the truck tires are built sacrifices friction of the tire (tires ability to adhere to the roadway surface) so they last longer
  • Truck tires are a harder, stiffer construction
  • Truck tires are exposed to high temperatures and high psi
36
Q

What has a significant impact on the friction value?

A

Slope, Tire compound, Vehicle braking efficiency, Loose material on the surface

37
Q

What is necessary when determining a vehicle’s percent braking efficiency?

A
  • The percent braking efficiency at each wheel or axle

- The weight distribution at each wheel or axle

38
Q

What does the friction circle represent?

A

The maximum longitudinal (braking and acceleration) and maximum lateral (left and right turn) friction capabilities of a vehicle

39
Q

The result of both braking and turning friction can be determined by _______ ___ ________ ____ of the lateral and longitudinal friction values

A

adding the vector sum

40
Q

What happens if a vehicle exceeds the maximum lateral and longitudinal friction values?

A

The vehicle will lose traction

41
Q

The Energy Method for calculating velocity is based on what?

A

The Work-Energy theorem

42
Q

Break down the units in Work

A

W=wfd
W=(pounds)(unit-less)(feet)
W = Foot-Pounds or Ft-Lbs

43
Q

True or False: The Energy Method for calculating velocity should be used in a situation where the vehicle movement is simple.

A

FALSE - It should be used when the vehicle movement is complex

44
Q

What information is required to conduct an energy analysis of a vehicle?

A
  • A scaled physical evidence and dynamics diagram
  • A full understanding of the motion of the vehicle
  • The distance each wheel traveled over each surface
  • The vehicle-weight distribution
  • The coefficient of friction or drag factor over each surface
45
Q

The energy calculated from an impact (change in velocity) can be ________ __________ ___ the energy calculated from the movement prior to impace

A

added directly to

Energy is added
Velocity is combined

46
Q

The energy calculated from an impact (change in velocity) can be ________ __________ ___ the energy calculated from the movement prior to impace

A

added directly to

Energy is added
Velocity is combined

47
Q

The basic speed equation is an _________ _________ to the work done over the distance under study

A

Energy Equivalent

48
Q

The basic speed equation is based on the _______-_______ theorem

A

Work-Energy

49
Q

True or False: The speed calculated using the basic speed equation is the speed the vehicle was traveling at the beginning of sliding

A

TRUE

50
Q

A speed calculated using the basic speed equation must be ________, ________ ___ _________ _______ _______ _____ velocities calculated over multiple surfaces

A

combined, using the combined speed equation with

51
Q

What are characteristics of a Critical Speed Scuffmark?

A
  • Arced
  • Striations
  • Outboard front wheel tracks inside of outboard rear wheel
  • Outboard front wheel will generally mark first and be darker than outboard rear wheel
  • Prior to broadside there will generally be two tire marks
  • Outboard tires continue to separate to broadside, unless equipped with ABS
  • Decreasing radius
  • Thin to wide
  • 20 degrees or 1/3 wheelbase
52
Q

When does a CSS become a side skid?

A

When the vehicle has over a 20 degree sideslip angle or when the front and rear wheels on the same side of the vehicle are separated by approximately 1/3 the wheelbase

53
Q

What is side slip angle

A

The angle between the heading direction and the vehicle’s center of mass path of travel

54
Q

The _________ the chord, the _________ the mid-ordinate measurement, therefore, the greater sensitivity to error in determining the radium and subsequently the speed.

A

Shorter

Smaller

55
Q

The chord should never be shorter than _______ feet.

A

25

*Per SAE paper, 30 feet

56
Q

What should be used when calculating velocity based on CSS?

A
  • The radius of the center mass path of travel of the vehicle
57
Q

When using the critical speed equation, the slope adjustment to the drag factor should be measure along what?

A
  • Along the path of slippage which is parallel to and in the direction of the striations
58
Q

A CSS is made by a rotating or non-rotating wheel?

A

Rotating

59
Q

True or False: The Critical speed equation calculates the minimum speed of the vehicle where the tire marks are being made.

A

FALSE
The critical speed equation calculates the average speed of the vehicle where the tire marks are being made over the distance of the cord

60
Q

True or False: Speed determined from TFMs made after the CSS can be added to the speed determined using the critical speed equation.

A

FALSE

Speed determined from tire friction makes made after CSS can only by COMPARED to the speed determined from the CSS.

61
Q

When and how can speed be added to the speed calculated from the critical speed equation?

A

Speed determined from TFMs made BEFORE CSS can be added using the kinematic equations or the combined speed equation

TARSC (6 decks)

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