Take a long cylindrical balloon and, with a thin felt-tip pen, mark a small square on it. What will be the shape of this square after you blow up the balloon: (1) A larger square, (2) A rectangle, with its long axis in the circumferential directions, (3) A rectangle, with its long axis in the longitudinal direction, or (4) An ellipse? Perform this experiment and, based on your observations, explain the results, using appropriate equations. Assume that the material the balloon is made of is perfectly elastic and isotropic, and that this situation represents a thin-walled, closed-end cylinder under internal pressure.