# Homework Help: Dynamics and Batman

1. Oct 20, 2008

1. The problem statement, all variables and given/known data

I am trying to show that the Batman scene where the tractor trailer flips over the long way is completely unreasonable.

I would like to use, as a very simple model of the problem, Principle of Impulse and Momentum.

So please help me out. I have a truck traveling at some constant velocity. It drives straight into a "trip wire" tied across the road to two lamp posts. Now, assuming that the lamp posts and the wire and the truck do not fail and fall to pieces, I would like to find out how fast the truck would have needed to have been going in order to create a moment about the wire.

Could I have a little assistance in setting this problem up?

I know that the trucks momentum could be said to act at the Center of mass. Is the point on the truck where the wire strikes a "force" ? And how so I find its magnitude (dude)?

The scene is http://www.youtube.com/watch?v=81LeooTiKI0" for those who have not seen it. It's at 0:45 seconds

Last edited by a moderator: Apr 23, 2017
2. Oct 20, 2008

Any ideas? It's the "is there a force where the wire strikes?" part that is really getting me...

3. Oct 20, 2008

### Stovebolt

There is certainly a force where the truck strikes the wire. I think this may be part the unknown that you are trying to find.

I would think that a good starting point would be to consider the energy of the truck and the distance over which the wire acts on it. Also, assuming the wire is below the center of mass of the truck, you should have created a moment to induce rotation.

To get the numbers to work out, you will likely have to find the moment of inertia of the truck about the appropriate axis.

Hope this helps, let me know if you come up with a good problem.