I solved the following problem and got 48.2[sup]o[/sup] as the answer, but the provided answer is 60[sup]o[/sup]. Which is correct?

A small marble resting on the top of a hemisphere starts to roll down, without slipping. At what angle will the marble become airborne?

[img]http://www.phy.ntnu.edu.tw/ntnujava/index.php?action=dlattach;topic=1378.0;attach=1546[/img]