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Level 82

Collisions


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impulse
a large change in momentum over a short period of time
kinetic energy
a running dog
Conservation of Linear Momentum (CM)
CM → m₁u₁+m₂u₂ = m₁v₁+m₂v₂
NEL → − e = (New Velocity) ÷ (Old Velocity)
Newtons Experimental Law for impacts (NEL) (a ball hits the ground)
e = 1
Coefficient of Restitution, e for an perfectly elastic collision:
e = 0
Coefficient of Restitution, e for an perfectly inelastic collision:
0 ≤ e ≤ 1
Range of value that "e" can have:
Newtons Experimental Law (NEL):
NEL → − e = (v₁ − v₂) ÷ (u₁ − u₂)
Solve: Direct Collisions ( only in one direction)
Use 1. Conservation of Momentum. 2. Newton's Law of Restitution. 3. Simultaneous Equations.
Solve: Oblique Collisions at impact the centres are aligned in the "i" direction.
Use the CM and NEL on the "i" components. The "j" components are unchanged.
Solve: Oblique Collision at impact the centres are at an awkward angle. Find the angle:
Draw a good diagram of the moment of impact. Form a right angled triangle between the centres. The Hypotenuse = 2r.
Have your diagram clearly. Physically rotate the page. Draw your new "i" and "j" components.
Solve: Oblique Collision at impact the centres are at an awkward angle. Rotate the coordinate system:
Solve: Oblique Collision: the angle through which the sphere is deflected:
Get the slopes of the initial and final vectors. ( Slope = "j comp" / "I comp"). Use the formula: Tan θ = ± (m₁ − m₂) ÷ (1+m₁ m₂).
Potential Energy:
Ep = mgh
Collisions with Strings (like Newtons Cradle)
Use Conservation of Energy: Lost Potential Energy = Gained Kinetic Energy to find the velocity at impact.
Gap skid
At least 10 feet skid apart caused by releasing break
Skip skid
1-3 foot gap cause by bouncing, pedestrian impact, or pot holes. Interrupted skid
Damage classification
No damage
Impeding skid
Ghost like skid, caused by locking of breaks. Not quite leaving a skid.
Curved skid
Caused by road sloping, unequal breaks, unequal road surface. Measure full length of skid. Do not go in straight line
ABS skid
Skids that go from light to dark to light to dark. Continuously interrupted by breaking system.
Overlapping skid
Cause by all 4 or 2 tires on one side locking up. Measure entire length and subtract the wheel base.
Spin skid
Caused by vehicle spinning. Measure entire length as on surface.
Crook/scrub
Sudden change during skid because of impact. Noted as collision scrubs.
On map road component
1 tenth mile/ 500ft on straight level road.
Injury categorization
No injury
Strategy driving
Rarely requires quick decision making
Tactic driving
Requires quick decision making. Actions taken by driver to avoid collision.
Reaction time
1.6 seconds. My be affected by age, strength, physical condition, habits, and perception delays.
People
Components of highway transportation system
Id
4 kinds of info doc for each
Driver
People component 5 categories
Operational
Collision causes
Operational factors
Driver has control over
Conditional factors
Driver has no control over
Concentric collision
Impact in center mass. Little or no rotation
Eccentric collision
Impact not in center mass resulting in rotation after impact.
Major events of collision
Point of possible perception
Point of actual perception
Not present in all collisions
Skill
Level 1-3
Science
Level 4-5
collision
A situation in which two objects in close contact exchange energy and momentum
Accident
Sequence of events that usually produce unintended injury, death or property damage.
Contact force
A force that "touches" or comes in contact with the system
Energy
(physics) the capacity of a physical system to do work
Field Force
A force exerted on an object without touching it
force
(interactions between two objects)
friction
a contact force; type of force between two touching surfaces
gravity
(physics) the force of attraction between all masses in the universe
heat
transfer of energy due to a difference of temperature. The form of energy that is transferred between two substances because they have different temperatures.
independent variable
The variable changed on purpose in an experiment; all others should be kept the same.
inertia
_______ is the property of an object that leads it to resist any change in motion
net force
Acceleration depends on the
acceleration
(physics) a rate of change of velocity
balanced
adj. in a state in which equal and opposite forces cancel each other out
Potential Energy
(mass) x (g) x (height)
Power
(physics) the rate of doing work
dependent variable
Changes in this variable need to be measured in an experiment; its value should change due to intentional changes in another variable.
Speed
Units: cm/s, m/s, mi/hr, km/s ...
support
lift, in the air (planes/birds)
Unbalanced
Unequal forces acting on an object is a _______ force.
energy transformation
A change from one form of energy to another is called_______
artery
A major blood vessel which carries blood away from the heart to the rest of the body.
Conservation of Energy
Energy cannot be created or destroyed; it may be transformed from one form into another, but the total amount of energy never changes
uniform
Describe the tension in a freely running massless rope
vein
A major blood vessel which carries blood back to the heart from the lungs or from the body.
weight
A force that comes from gravity pulling down on any object with mass
work
a force acting upon an object to cause a displacement. (key words: force, displacement, and cause)