1. The problem statement, all variables and given/known data A small block starts at rest on top of a frictionless hemisphere (like an igloo) of radius 1.7m. Then the block slides down from the top. At what height above the ground (in m) is the block moving fast enough that it leaves the surface of the hemisphere? 2. Relevant equations mv^2/r = a mgh = PE .5mv^2 = KE 3. The attempt at a solution I think that the thing will leave the surface when the centripetal force is greater that the force of gravity, because the force of gravity is the only force supplying the centripetal force. So, (mv^2)/r > mg so v>sqrt(rg) The velocity after falling a height h is v=sqrt(2gh) sqrt(2gh)>sqrt(rg) 2gh>rg 2h>r h>r/2 so it would have to fall 1.7/2 = .85m .85m is not the correct answer. The only other thing I can think of is that the force supplied by gravtiy varies based on the angle that the normal force between the object and the cube changes.