how have advances in technology affected the safety of vehicles?
TRANSCRIPT
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?
Overview Forces acting on your car and body in a car
crash
Physics of moving objects
Newton’s Laws of Motion
3 types of collisions that occur during a car crash
Causes of car crashes
Vehicle safety
Is how much matter is in something.
The more you stuff in your suitcase,
the more massive it becomes.
Is how fast something
is traveling.
Direction is not important !
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.
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.
Newton’s 2nd Law of Motion
Force equals mass times acceleration
is a push or a pull.
F = ma
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.
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 can’t move his legs, but still scores for SA and wins the game!
The announcer says the player’s
carried him over the goal line.
is in
motion !
All objects have mass.
If an object is moving, it has momentum.
Momentum = mass x velocity
Momentumand its relationship to mass and speed
Suppose the 150 lb Starkville Academy running back has a speed of 10 mph going east.
They collide head on at the goal line.
What are the results ?
Suppose the 100 lb Heritage Academy line backer has a speed of 10 mph going west.
The Starkville Academy player has a mass of 150 lb and is running 10 mph toward the
east.His momentum is 1500 lb mph east
The Heritage Academy player has a mass of 100 lb and is running 10 mph toward the
east.
His momentum is 1000 lb mph
west The result is a final momentum of 500 lb
mph east (towards the goal line).
Momentum = mass x velocity
x timetime
the force is applied
A moving car has momentum.
When this car crashes, it’s momentum is changed.
A change in momentum is called an
is an applied
over a period of timetime
.
.
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.
Inertia
Without a push or a pull, an object at rest remains at rest and an object in motion remains in motion.
Newton’s First Law of Motion
Newton’s 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.
What causes vehicle crashes? Speeding Too many lane changes Following too closely Running red lights Distractions Driving while under the influence
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
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.
Car CrashCar Crash
More stoppingtimetime
means
In a
the stopping timetime
is
by having a
front end and bumper on the car.
The Human Collision
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).
At the moment of impact, passengers in the automobile are still traveling at the vehicle’s original velocity.
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.
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.
What happens when two objects collide?
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.
Influences:
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
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
Sometimes anair bag
or seatbelt is used to
stop the passenger
No airbag
No seatbelt
No seatbelt with baby
Hit fromHit frombehindbehind
Seat beltsSeat belts
Bumpers The bumper’s purpose is to absorb crash energy
without significant damage to the bumper itself and no damage to the vehicle’s 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.
Distance it takes to safely stop a car
Speed(mph)
Reaction Time
(ft)
Breaking Distance
(ft)
Total Stopping
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
“I don’t 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,
don’t forget that seat belt! 11 percent of all fatal crashes occurred when
the car was going 30 mph or less.
How many times have you heard people say…
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
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?
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?
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: Newton’s 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/ CLASS/ 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/ Class/ 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/ physics/ phys01/ accident/ default.htm
Zobel, E. (1997). Newton’s second law of motion. Retrieved March 2, 2008, from http://id.mind.net/ ~zona/ mstm/ physics/ mechanics/ forces/ newton/ newtonLaw2.html