PARIS, France (Reuters) — Do you want to know how fast a tennis ball goes? Zip down a line strung from the second floor of the Eiffel tower, 115 meters above the ground. During the French Open and in association with tennis tournament Roland-Garros, bottled water vendor Perrier allows volunteers to down at 90 km/h, the speed of a tennis ball being smashed. Volunteer Julien Bidet, 39, said he both feared and loved the experience, […]