[ajbrown]

Originally Posted by RickeyD

Mythbusters on Head-on Collisions – Greg Laden's Blog

Fun show.... here is the short clip pertaining to this subject...

Mythbusters Car Crash Force

[tuccillo]

Yes, correct. The important point is a collision into a substantial wall where the vehicle has to absorb virtually all of the energy. For the head-on collision, the important point is that both vehicles collide directly into each other and the combined KE is equally absorbed by both vehicles. In that case, it is as if both vehicles collided into a wall.

Originally Posted by chuckinca

From Wikipedia:

While it is true (via Galilean relativity) that a head-on crash between two vehicles traveling at 50 mph is equivalent to a moving vehicle running into a stationary one at 100 mph, it is clear from basic Newtonian Physics that if the stationary vehicle is replaced with a solid wall or other stationary near-immovable object such as a bridge abutment, then the equivalent collision is one in which the moving vehicle is only traveling at 50 mph.,[3] except for the case of a lighter car colliding with a heavier one.

.

[tuccillo]

I hadn't seen that before. That pretty much proves it.

Originally Posted by RickeyD

Mythbusters on Head-on Collisions – Greg Laden's Blog

[RickeyD]

Originally Posted by tuccillo

I hadn't seen that before. That pretty much proves it.

Mythbusters rule.

[tuccillo]

Yes, they do. I have always been impressed by the fact that they practice good experimental design. For an "entertainment" show, it would be easy for them to be a bunch of hacks but they always seem to run well thought out controlled experiments. Besides the fact that they are pretty funny, I believe that is why they have lasted so long.

Originally Posted by RickeyD

Mythbusters rule.

[Polar Bear]

Originally Posted by tuccillo

...Oh, and you can skip the personal insults.

You're kidding, right?

Have you even read your posts? Condescending and insulting...to anybody reading them.

[joldnol]

I wish my former students had you guys enthusiasm.....great debate. Sadly Mythbusters is kaput after this season

[rubicon]

Originally Posted by kathy and al

The road signs at the corner of Morse and San Marino clearly show that the golf cart has the right of way. Why??? Don't know but would entertain the possibility of changing this so that the auto driver has the right of way. Golf cart drivers--please--no nasty comments. Thanks

kathy and al: I appreciate your point of view. However perhaps if you were introduced to the guy (cart driver) who was broadsided by a car striking his leg and causing him months in the hospital and more months in rehabilitation you might change your mind about who should have the right of way (row)

Personal Best Regards:

[rubicon]

Originally Posted by suesiegel

I'm not pro regulation BUT
In my view the golf carts should have some form of ID-plates?
The LAW is that to drive a cart without plates means it is speed restricted to 20 mph.
I am often passed by carts doing at least 25-30. THEY ARE ACTUALLY DESIGNED TO DO 15 MPH. You only have brakes on the rear wheels.
There are some interesting drivers here. Turn signals are to signal you intend to make a turn-USE THEM. Follow the LAW. Stopping in the middle of the road to BS is common but is STUPID-you can cause an accident-PULL OFF THE ROAD.

Hi suesiegel: Speed is a catchall for all accidents but it doesn't explain inattention, misjudgments distractions ,etc. I have not been around a cart going 30mph however let's suppose a cart is maintaining that speed in a diamond lane when a car comes along drifting into the carts lane striking the cat driver. Is speed the cause?

[rubicon]

Originally Posted by Rapscallion St Croix

It doesn't work that way. What you get is the equivalent of hitting a solid wall at 20MPH.

Yep your right

[tuccillo]

Nope, just to you because you act like a know it all when you are actually wrong. Aren't you the one who said "go read a physics book"? How rude and condescending it that ? Well it turns out you are wrong.

Originally Posted by Polar Bear

You're kidding, right?

Have you even read your posts? Condescending and insulting...to anybody reading them.

[Arctic Fox]

Originally Posted by Arctic Fox

don't forget that we are dealing with energy here, not momentum

momentum is mass x velocity: m x v

kinetic energy is "half m v squared": 0.5 x m x v x v

so, a cart of mass 1 going at speed 20 hitting a brick wall dissipates kinetic energy of 0.5 x 1 x 20 x 20 = 200 units

whereas a cart of mass 1 going at 40 hitting a brick wall dissipates kinetic energy of 0.5 x 1 x 40 x 40 = 800 units

double the speed, and you quadruple the kinetic energy because of the squaring

assuming the two carts are of equal mass and hit head on, the combined dissipated kinetic energy is 200 + 200 = 400 units

it does not matter whether a cart hits another cart head on or a wall - if it is brought to an immediate stop then the kinetic energy dissipated per cart is the same (200 units)

so two carts hitting each other head on, each doing 20, dissipates only half the kinetic energy (400 units) of one cart hitting a wall at 40 (800 units)

[Polar Bear]

Originally Posted by tuccillo

Nope, just to you because you act like a know it all when you are actually wrong. Aren't you the one who said "go read a physics book"? How rude and condescending it that ? Well it turns out you are wrong.

"I will do the mathematical proof but I am not sure anyone will follow it." - your words. Yeah...that's not condescending and insulting at all.

And I'm only wrong in your mind. I know it's futile to reply, but I will anyway. You are talking about the net damage done in two totally different scenarios. The net damage done may well be roughly the same in both. Heck, I'm a big fan of Mythbusters, and I don't see anything in there that I disagree with. I am simply saying that relative speed does matter...a lot!

Why don't you comment on the thought problem I posted earlier...

Scenario 1 - A solid wall, block, whatever is moving along at 20 MPH and hits a stationary wall.
Scenario 2 - Two solid walls, blocks, whatever are moving toward each other, each going 20 MPH, and collide.

Are the collisions identical in every respect? Of course not. There is much more energy in Scenario 2. I've said nothing that conflicts with this in any of my posts. I'm only stating that two vehicles colliding at 20 MPH is not identical to a vehicle traveling at 20 MPH hitting a stationary wall, even if the net damage is similar.

[TNLAKEPANDA]

What the heck is going on here?

[RickeyD]

Occum's razor now applies. Time out Newtonians