I feel like this is a really basic question but I'm struggling to come up with a straightforward answer!
In this video:
We see a 10 foot knife dropped from 30 feet onto a car. It pierces straight through the car and only stops when it hits the ground.
I can calculate the easy stuff, such as the gravitational potential energy of the knife before being dropped, its velocity and momentum at the moment it reaches the car, impact force on the ground etc. but I need to explain how it's able to pierce so easily through the car.
I believe it's because of the pressure applied by the point of the knife, but I can't seem to calculate anything to do with force applied to car or energy transfer from the knife to the car, as it doesn't look like it slows it down at all really.
I've looked a bit at the physics of ballistics but can't find anything that applies to this situation. Can anyone help?
I'd quite like to be able to work out how many cars the knife would go through if it weren't for the ground, but I feel like I'd need quite a lot of information to calculate this, e.g. the density of the car's body, and the knife, area and thickness of the knife et cetera.
I don't know anything at all about the 'physics of cutting' so I am at a bit lost!