# How many Newtons would it take to damage a car?

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1. Feb 1, 2016

### Alexander Baine

I am working on a science project, just in my spare time, and for this project I needed to know the amount of force it would take one car to damage another car, but the same model (so same weight, strength etc.) thanks for you help

~ Alex

2. Feb 1, 2016

### Hesch

Say we are speaking of a head-on collision. If the lengths of the cars are compressed 2 m, the cars are damaged.

Say the speed of the cars is 100 km/h and the weight of the cars is known, you can calculate the mean decelleration and thus the force needed to bring them to a halt.

3. Feb 1, 2016

### jbriggs444

Professionals do this with crash tests. You cannot do it with physics. There are too many unknowns. It is an engineering problem. After a head-on crash that appears to result in no damage, energy absorbing bumpers may, in fact, have suffered irreversible changes. The next crash may not be as pretty.

4. Feb 1, 2016

### A.T.

"Damaged" is a bit of understatement here.

5. Feb 1, 2016

### Hesch

Say we are speaking of a head-on collision. If the lengths of the cars are compressed 2 m, the cars are damaged.

Say the speed of the cars is 100 km/h, the weight of the cars is known, you can calculate the mean decelleration and thus the force needed to bring them to a halt.

Sorry, I don't think I have posted the above, which is just a repetition of #2. Some technical error ?

Last edited: Feb 1, 2016
6. Feb 1, 2016

### Staff: Mentor

Which part of the car is easiest to damage? The glass should be pretty easy, but I'm guessing that I can get a door panel to buckle by just pressing hard enough on it manually in the middle. If not, I'm sure I can do it by kicking. Better yet, I can "key" a car with almost no effort at all. So, if a one car scrapes the other car with virtually no force, damage will be done. Does this answer your question?

Last edited: Feb 1, 2016
7. Feb 1, 2016

### bcrowell

Staff Emeritus
Force by itself is not going to be enough to predict damage. It depends on the area that the force is spread over, and it also depends on the time derivative of the force. (A constant force can't cause vibration, whereas a varying force can.)

8. Feb 1, 2016

### alw34

What not use a different object...something other than a car....
Perhaps you can find a table that shows deformation characteristics of some simplier objects...a quick search did not turn up anything exciting.

I know different construction materials are rated for various loads....say 2" x 4" studs or 4" x4" posts [typically wood]. And I'm sure lally columns are similarly rated....

You might consider, for example, firing a pair of 2" x4" x8ft' pieces of lumber at each other and seeings if you can estimate some small initial deformations....

https://en.wikipedia.org/wiki/Compressive_strength

How far must a basket ball be dropped to deform 1" ? I have no idea; but you could could try figuring it out assuming a vacuum so there is no air resistance slowing it down....

9. Feb 3, 2016

### Svein

I expect the pressure at a given point of the car is more important than the force. I know (I have seen it) that it is possible to drive an awl through the bodywork by force of hand alone. The same force applied to a large object (say the hand itself) does almost no damage.

10. Feb 3, 2016

### Staff: Mentor

This is pretty much the same thing bcrowell said in post #7 and is also similar to what I said in post #6 when I talked about "keying" a car.

11. Feb 3, 2016