How have advances in technology affected the safety of vehicles?

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?

Car Crash Physics By Lisa Atwell

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

The Physics of Moving Objects momentum Impulse Velocity Speed time Mass Acceleration

Is how much matter is in something. MASS 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. 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 !

Speed is distance time

Is how fast something is going and Velocity Speed Is how fast something is going and in which direction. + direction

Velocity is distance direction in a time 55 mph south

When a car accelerates, it may be speeding up or slowing down. Acceleration is Speed the change in When a car accelerates, it may be speeding up or slowing down.

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.

Experiment #1 Velocity or Acceleration?

Newton’s 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.

Do you know the word that describes a MASS in motion ?

Here is a clue: omentum m 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 omentum m carried him over the goal line.

in motion ! Momentum = mass x velocity momentum MASS is All objects have mass. If an object is moving, it has momentum.

Momentum and 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 ?

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).

time time Impulse Force . Impulse Impulse Force . x 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 Impulse Impulse is an applied Force time . over a period of

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.

Experiment #2 Egg Toss Stop that egg!

In the car’s collision, the Force Determines the amount of damage to the car and the passengers

Inertia Newton’s First Law of Motion Without a push or a pull, an object at rest remains at rest and an object in motion remains in 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

to the car and driver is great. time If the to stop a is small, Force Then the stopping is LARGE damage and the to the car and driver is great.

time to stop a If the LARGE, Force the stopping small and the is is damage and the to car and driver is less.

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.

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

The Human Collision At the moment of impact, passengers in the automobile are still traveling at the vehicle’s 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).

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? 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.

What Helps Drivers and Passengers Survive Collisions? Air Bags Seatbelts Bumpers

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

But as the driver, please remember, Speed does kill.

Total Stopping Distance (ft) Breaking Distance (ft) 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 65 253.5 325 70 77 294 371 Longer than a football field

How many times have you heard people say… “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.

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

Would you jump? At 35 mph At 40 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?

Remember, More stopping time, means less force!!

Experiments Bumper Design Automotive Design Challenge Engineering Challenge

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