A simple gun can be made from a uniform cylinder of length  $L_0$  and radius  $r_0$ . One end of the cylinder is sealed with a movable plunger and the other end is plugged with a cylindrical cork bullet. The bullet is held in place by friction with the walls of the cylinder. Initially it is necessary to squeeze the bullet to get in to the cylinder in the first place. The bullet normally has a radius ‘r’ that is slightly larger than the inside radius of the cylinder. The bullet has a length $h<<L_0$ . The walls of the cylinder apply a pressure P to the cork bullet. When a pressure P is applied to the bullet along a given direction the bullets dimensions in that direction changes by $\Delta x$  such that $\frac{\Delta x}{x}=-\frac{P}{y}$ , where y is the young’s modulus of cork. The poison’s ratio for cork is zero such that we can assume that the compression along the direction does not cause expansion in any other direction. $P_0$  is the atmosphere pressure and $\mu$  be the coefficient of friction between cork and the cylinder. The temperature of the gas (air) inside the cylinder is  $T_0$.