[问答题]
A girl is whirling a ball on a26de4mbsp woa+6byp 0 string around her hea ;t::ts st )0yx;rxtedd in a horizontal plane. She wants to;xtx r eyd0ts t)s::;t let go at precisely the right time so that the ball will hit a target on the other side of the yard. When should she let go of the string?
