Hi! I was just wondering regarding this. When we swing a bob tied to a thread, completely perpendicular to the vertical wall (that is, parallel to the floor), what force balances the weight of the bob? I don't think it can be mv^2/r because that centripetal force is perpendicular to the weight of the bob (thus mv^2 cos90 = 0N). What force balances the weight of the bob? Thanks!