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Physics/newtons law



Using Newtons 3 laws of motion, how can i explain why the seatbelts should be used in a moving vehicle with logical arguments and scientific truths.


ANSWER: I'm in the hospital now (long story), so I'll make this brief.  Newton's laws state that you will be 1) moving in a straight line unless acted upon by an equal and opposite force.  If you happen to be strapped to a giant car while moving in a straight line then you will be subject to its rate of change of momentum, which will be much lower than if, say, you were to be ejected through a window and hit a really solid object.  Ouch!  Stitches.  They also say 2) That force = mass * acceleration.  Well, if you accelerate slowly, like the car with its crumple zones, you might accelerate less.  Especially if you're crashing into air bags.  And also 3)  That objects in contact exert equal and opposite forces on one another.  So seatbelts do bruise and injure you (just ask my mother) and should be held on really stiff springs to not catch so hard (some engineer just get working on that already), but essentially they still save you from going through glass, across pavement or into an oncoming vehicle, and dying in the bulk of cases.

Wear your belts, people.  Seriously.

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QUESTION: Hope you get well soon.

Thanks for the answer, but what i dont get is how acceleration can relate to car accidents and enforcing to wear seat belts... If the car is accelerating and crash into something, how could it affect the driver other than the fact of inertia playing a role?


Ummmm...I think you just answered your own question.  Inertia would be the primary problem in a crash.  Seat belts are designed to decelerate the moving human body relative to whatever the car is crashing into.  I'm not sure how that's not somewhat obvious or how to make it more obvious, really.


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Dr. Stephen O. Nelson


I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.


I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.

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