I'm an avid bike rider and a first year physics student. A couple days ago a friend of mine told me about how his friend was going downhill on her bike, used her front brake, and went over. I would like to determine what the minimum speed for a given slope angle is for the biker to do a full 180° rotation. Let's assume the slope is 30°, and the bike is a point-mass. I've given a shot at the problem but I feel like I'm walking in the dark here. Here are a few possible ways to think about the question: In terms of energy conservation principle: I think this is probably the most straightforward way to go about it, since we can draw a very clear picture of what's going on with very basic equation: Before rotation: Etotal = Elinear kinetic During rotation: Etotal = Erotational kinetic + Epotential - Elost from friction. This makes for some easy calculations. In terms of conservation of momentum: Since friction is applied though, I don't think momentum is conserved. In term's of Newton's equations of motions and torque: This seems like a plausible approach, except that for an object to rotate you need to apply torque. I drew force diagrams to try to see where the torque could come from but I simply don't. This hints at the fact that I don't understand why the bike turns over like this (my intuition tells me it does, of course, but I don't understand why). Could somebody give me some pointers for approach #3? Thank you!