Flashcards in TAR I Chapter Quizes Deck (61)
What is acceleration?
The rate of change in velocity with respect to time.
What is the acceleration equation?
Acceleration = change in velocity / change in time or delta v / delta t
What is constant acceleration?
A type of motion in which the velocity of an object changes an equal amount in equal time periods
How many basic values are considered in the kinematic equation?
Velocity - initial
Velocity - final
The kinematic equations are equations for motion with __________ ____________
What will cause a change in acceleration while a vehicle is in full braking?
A change in the surface
Do kinematic equations apply to a moving vehicle that is not braking or accelerating?
No, kinematic equations are only used when there is constant acceleration (either positive or negative).
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.
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
What are the three circumstances that will cause a Tire Friction Mark (TFM)?
- Extreme Acceleration
- Extreme Deceleration
- Extreme Changes of Direction
Describe a tire abrasion with smear
- A smear of tar/asphalt along with abrasions of tire material. They're long lived and most common on asphalt-concrete surfaces.
What is the primary marking mechanism on a Portland Concrete Cement (PCC) surface?
TRUE or FALSE: Erasing caused by a locked wheel tire is long lived/long lasting.
Name the four types of tire friction marks?
Critical Speed Scuff Mark (Yaw Mark)
Define a side skid TFM
A mark left by a rotating or non-rotating tire that is sliding or slipping sideways to its direction of travel
Define a locked wheel skid TFM
A mark left by a non-rotating tire that is sliding along its direction of travel
Define an Impending skid TFM
A mark left by a tire that is rotating slower than the forward velocity of the vehicle
Define a Critical Speed Scuff Mark (Yaw Mark)
A mark left by a rotating tire that is slipping sideways and diagonally to its direction of travel
What are characteristics of a CSS mark
- Starting thin and widening
Striations in a direction at an angle to the direction the vehicle is traveling
When does a CSS mark transition into a side skid?
- When the heading direction of the vehicle exceeds 20 degrees from center mass path of travel of the vehicle (or 1/3 the wheelbase).
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
B: The longest skid mark
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.
When might a vehicle be braking and the tire doesn't leave a TFM?
- 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)
Describe a gouge
- Occurs when strong metal components dig into the road surface.
Describe a chop
Deep gouges where chunks of the road surface have been dug out. A good indicator of maximum engagement
What are the three types of friction?
Describe Static Friction
The friction force when an object is just beginning to slide (i.e. trying to push a fridge)
Describe Dynamic Friction
Once the object is sliding, the force required for the object to continue sliding is less
Describe Rolling Friction
The resisting forces when a tire is rolling with no brakind