AP Physics
posted by AP Physics on .
A stone is tied to a string (length = 0.450 m) and whirled in a circle at the same constant speed in two different ways. First, the circle is horizontal and the string is nearly parallel to the ground. Next, the circle is vertical. In the vertical case the maximum tension in the string is 18.0% larger than the tension that exists when the circle is horizontal. Determine the speed of the stone.

mg+mv^2/r = 1.18(mv^2/r)
this should solve it, solve for v.
mg=.18mv^2/r
v= sqrt(r*g*.18) 
oops,
v= sqrt rg/.18
check that. 
what is the radius? how do we find that out