1. The problem statement, all variables and given/known data http://www.sumoware.com/images/temp/xzfrbardcbliotkt.png [Broken] A box travels in a circular track like the picture above. How much velocity it must have in point A to get out of the track when reaching point B ? 2. Relevant equations Fcentripetal = m V^2/R E = E' 3. The attempt at a solution First, I draw the free body diagram of the forces in point B http://www.sumoware.com/images/temp/xzstkkpbgobpmjmi.png [Broken] Actually, I want to draw the normal force, but I don't know where the normal force direction is. I know that the centripetal force is the force that's accelerating to the center. So, I think that Wb sin Θ is the same as the centripetal force. I use Wb sin Θ= F centripetal mg sin Θ= m v^2/r g sin Θ= v^2/r v = √(g r sin Θ) Then, I use the mechanical energy conservation formula. (I assume that the point A is zero in y axis) E = E' 1/2 mva^2 = mgh + 1/2 m vb^2 1/2 va^2 = gh + 1/2 vb^2 va^2 = 2gh + vb^2 va^2 = 2g(R+R sin Θ) + vb^2 va^2 = 2g(R+R sin Θ) + (√(g r sin Θ))^2 va^2 = 2g(R+R sin Θ) + g r sin Θ va^2 = 2gR+2gRsinΘ+gr sin Θ va^2 = 2gR+3gRsinΘ va^2 = gR (2+3sinΘ) va = √(gR (2+3sinΘ)) But, I'm not sure my answer is right. What I doubt is when I think the W sinΘ equals centripetal force and when I don't know where the normal force direction is pointing. Actually, I want to use ∑F = ma , but I just know the weight force to draw. Please help me.