Question

A student ties a 600.0 g rock to a 1.50 m-long string and swings it around her head in a horizontal circle. At what angular speed (in rev/min) does the string tilt down at a 13.1° angle, assuming that the local acceleration due to gravity is -9.80 m/s2?

Answer 1

weight/centripforce=tan13.1

mg/(mv^2/r)= tan13.1
solve for v

Answer 2

It says it was incorrect even after I converted to rev/min