|Why does a badminton birdie have such a large tip? Does making it bigger protect the racket? — J, California
The large, rounded head of a badminton birdie serves at least two purposes: it makes sure that the birdie bounces predictably off the racket's string mesh and it protects the strings and birdie from damage. If the birdie's head were smaller, it would strike at most a small area on one of the racket strings. If it hit that string squarely, the birdie might bounce predictably. But if it hit at a glancing angle, the birdie would bounce off at a sharp angle. By spreading out the contact between the birdie and the string mesh, the large head makes the birdie bounce as though it had hit a solid surface rather than one with holes.
Spreading out the contact also prevents damage to the racket and birdie. If they collided over only a tiny area, the forces they exerted on one another would be concentrated over that area and produce enormous local pressures. These pressures could cut the birdie or break a string. But with the birdie's large head, the pressures involved are mild and nothing breaks.