Momentum Analysis Flashcards
Newton’s First Law:
“A body at rest tends to remain at rest, while a body in motion tends to remain in motion in a straight line, unless acted on by an unbalanced external force.”
Mass
is the measure of the amount of material an object contains that causes it to have weight in a gravitational field.
Weight
the force exerted on a body by gravity.
Acceleration
is the rate change of velocity with respect to time.
Newton’s Second Law:
“The acceleration of a body is directly proportional to the force acting on that body, while it is inversely proportional to the mass of the body.”
Momentum
is the product of mass and velocity
Velocity and Speed:
Speed is a scalar quantity and velocity is a vector quantity
Velocity formulas require the units
to be in feet per second and are commonly used
in time and distance applications,
Static Friction:
The weight of a non-moving object, pressing down on a surface due to gravity, creates
Dynamic Friction
This is what we measure with a drag sled or a test skid.
Newton’s Third Law:
for every action there is an equal and opposite reaction
To perform a proper collision analysis the following should be conducted
- measure damage. 2. Photographs. 3. Reports by other investigators 4. The dimensions of the crash vehicles, 5. identify contact damage areas.
First Contact:
It is that instant where the objects first touch and force begins to develop between them.
Maximum Engagement:
It is at that instant, the vehicle and object have achieved a common velocity or are at the same speed, zero.
Last Contact:
Separation occurs when force between the colliding objects ceases, and the objects are no longer in contact or acting on one another.
Full Impact:
This occurs when some part of the colliding surfaces attains the same speed during impact.
Partial Impact:
Is when no substantial parts of the colliding surfaces attain the same speed during the collision.
Velocity Change:
The thrust or force between a vehicle and some other
object results in a collapse of parts of the vehicle.
This rotation is dependent on three things.
The strength and direction of the thrust
The point of application
Direction Change:
When the force is slightly eccentric and there is a full impact, the vehicle can’t continue in the same direction. When
Eccentric forces result in rotation.
the force is not directed towards the center of mass.
Collision between Vehicles in Motion:
A number of conclusions can also be made when two moving vehicles collide.
Damage and Movement:
Damage is a result of the forces of impact, which
deform the materials of the vehicles.
Damage and Speed:
In a two vehicle collision, the stronger vehicle
structurally will suffer the least amount of damage.
Damage and Thrust:
When vehicles make initial contact, the force of one
vehicle against another vehicle or other object, begins to crush parts of the vehicle in the direction of the thrust.
Contact Damage:
A thorough examination of contact damage areas can
reveal how the vehicles behaved during the collision.
There are two rules which govern this:
The greatest collapse in the contact damage area of each vehicle must be against the greatest collapse in the contact damage area of the other.
There are two rules which govern this:
Thrust directions must be in line, that is, the thrust of one must be directly opposite to the thrust of the other.
Principal Direction of Force (PDOF)
the summation of all collision forces required to deform the vehicle.
