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Insurance Safety Institute Vehicle Crash Tests

Added Dec 11, 2018 •

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please driver's boss control at very high speeds result was tragic for 1 driver unfortunate for the others but why what made the difference between walking away being carried away answer can be found in some of the most basic laws of the physical year hi my name is Griff Jones I teach High School physics and behind me is the Insurance Institute for Highway Safety vehicle Research Center it's a fascinating place where research Engineers assess the crash performance of vehicles by running tests and where they evaluate new technologies to prevent injuries like this state-of-the-art head protection system what's exciting for me is that this is a laboratory of practical applications in the subject I teach and because they're set up here to crash cars and analyze those crashes this Research Center provides a perfect venue for illustrating the physical laws govern the outcome of car crashes so follow me and for the next few minutes I'll take you behind-the-scenes but we can explore the basic science behind vehicle crashes my phone about car crashes and physics why does stomach get left behind is called inertia the property of matter that causes it to resist any change in its state of motion Galileo introduced the concept in the late 1500s and almost a hundred years later Newton use this idea to form play this first law of motion the law of inertia it's when the dummy fell off the back of the truck it was at rest and wanted to remain at rest that's inertia it's the same property that keeps a China on the table as you pull the tablecloth out from under it but what about a body in motion because your relationship to the passenger compartment my position isn't changing look at me from the outside you can see I'm going to keep on moving at the same speed external Force acts on me see how the car in the crash test dummy are traveling same speed now watch what happens when the car crashes into the barrier front end of the car is crushing and absorbing energy which slows down the rest of the car but the dummy inside keeps on moving at its Michelle speed until it strikes the steering wheel and windshield this is because a dummy is a body in motion traveling at 35 miles per hour and remains traveling 35 miles per hour in the same direction until acted upon by an outside force in this case is the impact with a steering wheel and windshield that applies a force that overcomes a dummies inertia inertia is one reason I see filter so important for nurses one reason that you want to be tired of the vehicle during a crash if you're wearing your seatbelt use flow down with the occupant compartment as a vehicle's front end does this job of crumpling and absorbing crash forces later we'll talk about how some Vehicles front ends for crumple zones do a better job of a Urban crash forces than others but for now let's get back to noon explain the relationship between crash forces and inertia in a second law and the way is often expressed is f equals in May the force f is what's needed to move the mass with acceleration a Newton wrote it this way it's the same thing acceleration is the rate at which the velocity changes multiply each side of the equation by T I get force times time equals mass times a change in velocity when you describe the relationship between force and inertia he actually spoke in terms of changing momentum with an Impulse what are these terms mean momentum is inertia in motion Newton to find it as the quantity of motion it's a product of an object's Mass it's inertia and its velocity or speed which has more momentum 80000 pound big rig traveling to miles per hour bar 4000 pound SUV traveling 40 miles per hour the answer is they both have the same momentum here's the formula PS4 Memento I don't know why I just do equals is for mass and B is for velocity equals MV that's momentum and what is it that changes an object's momentum it's called an Impulse it's a product of force and the time during which the force hats impulse was force times time is my favorite demonstration of impulse I have two eggs same mass I'm going to try to throw each egg with the same velocity that means they have the same momentum if the impulses are equal why do we have such dramatically different results play some big stopping force over a short time the sheet applies a smaller stopping force over a longer time. My students say that she has more to give to it. You can both decelerate experimental the zero print takes a smaller Forester is the experimental over a longer time in fact so much smaller that it doesn't even crack the egg shell now let's be like this to automobiles both of these cars have the same mass and both are traveling at the same speed 30 miles per hour like the eggs they have equal momentum as a result it will take equal impulses to reduce them into the zero 1 car will stop by Panic breaking in the other by normal braking drivers are belted so they decelerate with their vehicles the driver of the car on the bottom of experience more Force than the driver on top this is because of the impulses must be equal to decelerate each cars momentum the zero the driver that stops in less time or distance must experience a larger force and the higher deceleration a g is a standard unit of acceleration or deceleration people off refer to Jesus horses but they're not fighter pilots can feel as many as 9 G's when accelerating during extreme Maneuvers and astronauts it felt as many as 11 people in serious car crashes experience even higher G's and this can cause injury now consider what happens when a car traveling 30 miles per hour hits a rigid wall with shortens the stopping time or distance much more than Panic breaking let's assume the driver is belted and decelerates with a passenger compartment and let's also assume the car's front-end crushes one foot would uniform deceleration of the passenger compartment throughout the crash can this crash the driver would experience 30 jeans however if the vehicle's front end was less stiff so it crushed to steep instead of one the deceleration would be cut in half to 15 GS this is because the crush distance or the time the forces acting on the driver is doubled extending the time of impact is a basis for many of the ideas about keeping people safe and crashes it's a reason for airbags and bubble sounds in the vehicle you drive it's the reason for crash cushions and Breakaway utility poles on a highway man is the answer to the question I posed at the beginning of this film driver survived the crash because his deceleration from high-speed took place over a number of seconds best driver decelerate in a small fraction of a second and experience forces that are offered unsurvivable up to now we've been looking at single-vehicle crashes but if we look at two or more objects colliding we have to use another one of Newton's laws to explain the result even though the first cars would appear on the roads over 200 years collisions active topic of physics research in Newton's day back in 1662 Newton and his buddies for me one of the first international science club they call it the Royal Society of London for improving natural knowledge on the first experiments they did. test Newton's theories on collision using a device like this what do you think's going to happen when I release this ball a collides with the others I try to it's as if something about the Collision is remembered or say Newton theorize that the total quantity of motion when she call Momentum doesn't change its conserved this became known as a law of conservation of momentum and it's one of the Cornerstone principles of modern physics before we apply this to crash we need to know something else about momentum it has a directional property so we call Momentum a vector quantity this means if identical car is traveling 30 miles per hour Collide head-on cancel each other inside the passenger compartment of each car the occupants would experience the same decelerations from 30 miles per hour to zero the Dynamics of this crash will be the same as a single vehicle crash into a rigid barrier what conservation of momentum tells us about collisions of vehicles of different masses has important implications for the occupants of both heavier and lighter vehicle in a collision of two cars have unequal Mass the more massive car would drive the passenger compartment at the less massive car backward during the crash causing a greater speed change in the lighter car than heavier car these different speed changes occurred the same time so the occupants of the water car would experience much higher accelerations tents much higher forces than the occupant of the heavier car this is one reason why lighter smaller cars offer less protection enlarger heavier cars there's a difference between weight and size advantage and car crashes size helps you in all kinds of crashes weight is primarily an advantage in a crash with another vehicle it was a pretty brilliant guy Owosso most Advanced over 300 years ago are still used today to explain the Dynamics of modern-day events like car crashes Steven Newton failed to recognize the existence of energy all around us energy is Tonka conceptualize scientist had difficulty because it exists in so many different forms is usually defined as the ability to do work or is one of my students says it's the stuff that makes things energy comes in many forms there's radiant electrical chemical thermal and nuclear energy can relate to the concept of energy the car crashes though we're mostly cancer motion related energy kinetic energy moving objects have kinetic energy a baseball thrown to a batter a diver heading toward the water and airplane flying through the sky a car traveling down the highway all have kinetic energy energy doesn't have to involve motion an object have stored energy conformance condition this is a device that delivers a force to a crash dummies chest has a stiffness of the ribs the force is a result of a kinetic energy being transferred from the pendulum to the dummies as a pendulum status ready position is potential energy is equal to its kinetic energy at impact when it is released and begins traveling towards the dummies chest and potential energy transformed into kinetic energy if we freeze it halfway what is his potential vs. kinetic energy they are equal when is the pendulum reach its maximum kinetic energy here at the bottom of its swing the amount of kinetic energy an object has depends upon its mass and velocity greater the mass the greater the kinetic energy the greater the velocity the greater the kinetic energy formula that we use to calculate kinetic energy looks like this that's kinetic energy 1/2 Dam Square that's a velocity multiplied by itself if you do the math Cy speed is such a critical factor in the outcome of a car collision the kinetic energy is proportional to the square of the speed so if we double the speed required in Drupal the amount of energy in a car and energy is the stuff that has been how to do damage the connection between kinetic energy and force is that in order to reduce the car's kinetic energy and decelerating force must be applied over a distance that's work to shed for time how much kinetic energy requires either a decelerating force that's four times as great or four times as much Crush distance or a combination of the two the rapid transfer of kinetic energy is a car crash injuries so managing kinetic energy is what keeping people safe in car crashes is all about Brian O'Neill is the president of the Insurance Institute for Highway Safety that's incredible one of the things we do we put grease paint on the runs a vehicle Research Center and is one of the foremost experts in the world on vehicle safety turn crashworthiness to describe the protection of car offers its occupants during a crash that crashed were in this is a complicated concept because it involves many aspects of the open design the structure the restraint system adds up to the single term we used to illustrate the concept of good and poor structure designs for modern crashworthiness Bryan why is it important for the vehicle structure before Monica well this is what's left of the body and structure of a car that was in a crash in the use this to illustrate the point basically won the occupant compartment or the safety cage to remain intact we don't want any damage or intrusion into this part of the vehicle we want all of the damage of the crash complain to the front end looks the same it's actually different this the green Metals intended to crumple to give in the Collision turned into the car without allowing any damage to the occupant Apartments then the people inside can be protected against Serious injury basically want the front end to be buckling during the crash so that the occupant compartment is slow down of a gentler rate counting jumping off of a of a step and keeping your knees straight and waiting on the floor versus bending your knees when you land exactly the same concept so this is a vehicle that did well because there's very little in anywhere in the Octagon compartment these elements even though they're strong enough to hold an engine and suspension actually buckled and crushed just like they're designed to do so the damage is confined to the front end weather going to be like this in this is an example of a very poor safety cage this vehicle is in a 40 mile an hour crash and as you can see that the occupant compartment collapsed it's been driven backwards as a result the driver's space has been greatly reduced so someone sitting in this vehicle is obviously at a high risk of injury so even if the restraint systems do function properly the airbags and seatbelts the person is still is in grave danger this person in this vehicle even with a belt system in their bag is at significant risk of injury because the compartment is collapsing so it's analogous to shipping a box of China you can have all the best packing in the world around the China but if the boxes week you're going to break the chime when the safety cage collapses you going to have interest to the occupants look for Crossroads was in the same crash or team on an hour on 6th and you can see it now the safety cage has remained intact there's very little intrusion anywhere the damages find to the crumple zone of the vehicle this is the way it should be a person in a crash like this wearing their seatbelt and protected by the airbags from walk away from the crash with no injury by stand over here and I just looked towards the rear of the car and I ignore the airbag this doesn't even look like it's been in a crash that's right this is good performance good crashworthiness in our shipping box analogy this is an example of a strong box that's right the people in this box will be protected Brian obviously this car perform well for what's in the future for crashworthiness this is an illustration of how good we can do with public restroom but only part of the problem we obviously also have to pay attention to other crash codes what is the most important side effect rash that itches a vehicle that was in a severe side impact crash this week I was going 20 miles an hour or sideways into a pole and as you can see in a side crash you don't have all the crush space you having a frontal crash we just have the width of the door and the padding and in this case we have an airbag on the inside which creates even more space mean plate the airbag to create more Crush space and we also have an inflatable air bag to provide head protection this deploys from this roof area here so the physics of the same engineering challenges are greater I'm always looking for ways to relate to physics that I teach to the real world that my students experience and nothing is more relevant than traveling in an automobile you probably do it every day I hope that makes the message of this film important to each and everyone of you I always believed that if a person truly understand the laws of physics that person would never ride in a motor vehicle unbelted and now that you had a chance to learn from the finer points of a physic the car crashes I hope you're hungry I also hope you learn why some of the choices you make about the type of car you drive and the kind of driving you into it make a difference in whether you survive on the highway remember even the best protected race car drivers don't survive very high speed crashes all I know is that I'm a mix of a motor vehicle crash what happens to your car and you is determined by hard science you can't argue with the laws of physics

Uploaded by Debra Hood.

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Insurance Safety Institute Vehicle Crash Tests

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