We went to the Cavendish Laboratory to discover how fat you would have to be to stop a bullet. We used a gas gun, which is basically a huge air rifle. There is a chamber that is filled with high pressure helium (this is used because it is lighter than air so will expand more quickly).
The gun has a 3m long barrel which you load a small ball bearing into. There is a valve between the chamber and the barrel which can be opened very quickly. The gas (at about 70 atmospheres) then expands extremely rapidly forcing the bullet out of the barrel at supersonic speeds.
The gas chamber
The bulletA perspex tube was filled with gelatin, which is a similar density to fat, to act as the target.
A bullet hitting Gelatin
The bullet hits the gelatin at about 500m/s, that is over 1100mph - nearly twice the speed of sound!
While the bullet is passing through the jelly it creates a conical shaped hole behind the bullet. This is because to get out of the way of the bullet the jelly has to move very fast, and once the bullet has passed it will keep moving in the same direction expanding into a cone.
We have to say a huge thankyou to the Surface, Microstructure and Fracture Group at the Cavendish Laboratory. Particularly to David Williamson who set up the experiment for us despite his ridiculously busy schedule.
Comments
Add a comment