How have advances in technology affected the safety of vehicles?

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How have advances in technology affected the
safety of vehicles?
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Unit Questions

• What forces act on a car and on the body during a
  car crash?
• What are some causes of vehicle crashes?
• What are 3 types of collisions that occur during
  a car crash?
• How can vehicles be made safer?
• What can you do to be safe in a vehicle?

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Car Crash Physics

• By Lisa Atwell

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Overview

• Forces acting on your car and body in a car crash
• Physics of moving objects
• Newtons Laws of Motion
• 3 types of collisions that occur during a car
  crash
• Causes of car crashes
• Vehicle safety

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The Physics of Moving Objects
momentum
Impulse
Velocity
Speed
time
Mass
Acceleration
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MASS
Is how much matter is in something.
The more you stuff in your suitcase, the more
massive it becomes.
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Speed
Is how fast something is traveling.
Near your school, your mother presses on the gas
pedal to make the car go 15 mph (miles per hour)
On Interstate 82, your father presses on the gas
pedal to make the car go 70 mph.
Direction is not important !
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Speed
is
distance
time
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Velocity

• Speed

Is how fast something is going and in which
direction.

direction
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Velocity
is
distance
direction
in a
time
55 mph south
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Acceleration
is
Speed
the change in
When a car accelerates, it may be speeding up or
slowing down.
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Remember

• Mass is the amount of matter in something.
• Speed is how fast something is traveling.
• Velocity is how fast something is traveling in a
  direction.
• Acceleration is a change in speed.

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Experiment 1
Velocity or Acceleration?
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Newtons 2nd Law of Motion
F ma
Force equals mass times acceleration
Force
is a push or a pull.
This law means that while you are applying a
force on an object, it will continue to
accelerate or change its velocity. It also states
that the greater the force on an object, the
greater the acceleration.
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Do you know the word that describes a
MASS
in motion ?
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Here is a clue
The Starkville Academy running back is running
toward the goal.
The Heritage linebacker grabs his legs one
yard from the goal line.
The running back cant move his legs, but still
scores for SA and wins the game!
The announcer says the players
omentum
m
carried him over the goal line.
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momentum
is
MASS
in motion !
Momentum mass x velocity
All objects have mass. If an object is moving,
it has momentum.
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Momentumand its relationship to mass and speed

• Suppose the 150 lb Starkville Academy running
  back has a speed of 10 mph going east.

• Suppose the 100 lb Heritage Academy line backer
  has a speed of 10 mph going west.

They collide head on at the goal line. What are
the results ?
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Momentum mass x velocity

• The Starkville Academy player has a mass of 150
  lb and is running 10 mph toward the east.

1500 lb mph east
His momentum is

• The Heritage Academy player has a mass of 100 lb
  and is running 10 mph toward the east.

1000 lb mph west
His momentum is
The result is a final momentum of 500 lb mph east
(towards the goal line).
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Impulse
Force
time
x
the force is applied
A moving car has momentum.
When this car crashes, its momentum is changed.
.
A change in momentum is called an
Impulse
Impulse
is an applied
Force
time
.
over a period of
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Remember

• Mass is how much matter is in something.
• Acceleration is how fast you are changing your
  speed.
• Velocity is speed in a direction.
• A force is a push or a pull.
• Momentum is mass in motion.
• Impulse is the force times the time the force is
  applied.

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Experiment 2

• Egg Toss
• Stop that egg!

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In the cars collision, the
Force
Determines the amount of damage to the car and
the passengers
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Newtons First Law of Motion
Inertia
Without a push or a pull, an object at rest
remains at rest and an object in motion remains
in motion.
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Newtons 3rd Law of Motion
When object 1 pushes on object 2 with a force
object 2 pushes back on object 1 with the same
force
but
in the opposite direction.
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What causes vehicle crashes?

• Speeding
• Too many lane changes
• Following too closely
• Running red lights
• Distractions
• Driving while under the influence

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Have you ever wondered what happens inside a car
when it crashes?
In each car crash there are actually three
collisions
The Car's Collision
The Human Collision
The Internal Collision
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time
If the
to stop a
is
small,
Force
Then the stopping
is
LARGE
damage
and the
to the car and driver is great.
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time
to stop a
If the
LARGE,
is
Force
the stopping
is
small
damage
and the
to car and driver is less.
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Car Crash

• In a Car's Collision
• During a crash, the car crashes to a stop.
• At 30 mph, a car hitting an object that is not
  moving will crumple in about two feet.
• As the car crushes, it absorbs some of the force
  of the collision and increases the stopping time.

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time
Force.
More stopping
means
less
car wreck,
In a
increased
is
time
the stopping
collapsible
by having a
front end and bumper on the car.
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The Human Collision

• At the moment of impact, passengers in the
  automobile are still traveling at the vehicles
  original velocity.

• When the car comes to a complete stop the
  passengers continue to be hurled forward until
  they come in contact with some part of the
  automobile (the steering wheel, the dashboard,
  the front window or back of the front seat).

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• Humans in a crash can also cause serious injuries
  to other humans when they collide with each
  other.
• People in the front seat of a car are often hit
  by rear-seat passengers as they fly forward with
  incredible force.

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The Internal Collision

• In a crash, even after a human body comes to a
  complete stop, its internal organs are still
  moving.
• Suddenly, these internal organs slam into other
  organs or the skeletal system.
• This "internal collision" is what often causes
  serious injury or death.

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What happens when two objects collide?
Influences

• Mass
• Velocity
• Time

• Momentum
• Impulse

• The impulse experienced by the car equals a
  change in momentum.
• As car designers, we only have control over mass
  and time.

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What Helps Drivers and Passengers Survive
Collisions?

• Air Bags
• Seatbelts
• Bumpers

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Seatbelts

• Purpose is to restrain passengers from tossing
  back and forth after a collision
• Lap belt protects the pelvis and the shoulder
  belt protects the rib cage
• Have ability to extend and retract, but in a
  collision the belts will suddenly tighten up and
  hold passengers in place

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Air Bags

• Purpose is to slow down passengers speed after a
  crash
• A soft pillow to land against in a crash
• Works within a fraction of a second

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Sometimes an
air bag
or seatbelt is used to
No airbag
No seatbelt
No seatbelt with baby
Hit from behind
stop the passenger
Seat belts
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Bumpers

• The bumpers purpose is to absorb crash energy
  without significant damage to the bumper itself
  and no damage to the vehicles rear or front end.
  
• Low speed crashes mostly occur in urban traffic.
• Less damage is done in a collision when 2
  vehicles are lined up bumper to bumper.
• Bumpers can protect other components of a
  vehicle.

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But as the driver, please remember,
Speed
does kill.
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Distance it takes to safely stop a car
Total Stopping Distance (ft)
Speed (mph)
Reaction Time (ft)
Breaking Distance (ft)
10 11 6 17
20 22 24 46
50 60.5 181.5 242
65 65 253.5 325
70 77 294 371
Longer than a football field
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How many times have you heard people say

• I dont need to buckle up.
• I am just going around the block.
• I was just going 30 mph.

• While it is true that slower speeds reduce the
  risk,
• dont forget that seat belt!
• 11 percent of all fatal crashes occurred when the
  car was going 30 mph or less.

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Think of the following scenarios, when you make
that choice to use your seat belt

• At 3 mph
• Imagine that you are hit head-on by a football
  tackle running 3 mph. He knocks you flat and your
  head hits the turf. You wake up in the hospital
  with a serious concussion and a sprained neck.
• At 15 mph
• Imagine shoving your face into the windshield or
  your chest into the steering wheel at that speed,
  with no helmet, no pads, and no chance to brace
  yourself

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• At 35 mph
• You are driving at 35 mph when a deer darts in
  front of your car. You brake quickly, miss the
  deer and keep your car on the road. Shaken up,
  you pull over. An officer stops to offer
  assistance and then issues a citation for not
  buckling up. "Next time, you might not be so
  lucky, he says.

• At 40 mph
• Suppose you stand on top of a five story building
  and fall off head first.
• This represents 40 mph.
• Would you jump?

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• Remember,
• More stopping time,
• means
• less force!!

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Experiments

• Bumper Design
• Challenge
• Automotive Design
• Engineering Challenge

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Questions

• What are the three types of collisions that occur
  during a car crash?
• What are some causes of car crashes?
• How can you remain safe in a car?

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Resources

• CAVS Outreach Program, Cuicchi, P., Cuicchi, R.
  (n.d.). Mission eggcellence challenge
  Brochure. (Available from Center for Advanced
  Vehicular Systems, Mississippi State University)
• Henderson, T. (1996). Lesson 4 Newtons third
  law of motion. In The physics classroom
  tutorial. Retrieved March 2, 2008, from
  Glenbrook South High School Web site
  http//www.glenbrook.k12.il.us/?GBSSCI/?PHYS/?CLA
  SS/?newtlaws/?u2l4a.html
• Henderson, T. (1996). Speed and velocity. In The
  physics classroom tutorial. Retrieved March 2,
  2008, from Glenbrook South High School Web site
  http//www.glenbrook.k12.il.us/?GBSSCI/?PHYS/?Cla
  ss/?1DKin/?U1l1d.html
• Wirt, S. (1999). The physics zone Forces,
  accelerations, and car accidents. Retrieved
• March 2, 2008, from Oswego City School District
  Web site http//regentsprep.org/?Regents/?physic
  s/?phys01/?accident/?default.htm
• Zobel, E. (1997). Newtons second law of motion.
  Retrieved March 2, 2008, from http//id.mind.net/
  ?zona/?mstm/?physics/?mechanics/?forces/?newton/?
  newtonLaw2.html