1. The problem statement, all variables and given/known data Two smooth planes are joined at one end so that they form a V shape. The join is such that a mass placed on one of the planes will slide smoothly down one side of the V and then move up the other side. Find the period of the motion (T) of such a mass in terms of x0 (the initial horizontal position) and θ (the angle between each of the planes and the horizontal. 2. Relevant equations The potential energy in terms of horizontal position and hence the force and acceleration. 3. The attempt at a solution The potential energy of the mass on the LHS of the well seems to go like... V(x) = m.g.(x0-x).tan(θ) where x is the horizontal displacement from x0. I set things up like this to give V(x) = 0 when the mass is at the lowest point. and by differentiating I get a horizontal force m.g.tan(θ) towards the centre and an acceleration of g.tan(θ). Since the mass is uniformly accelerated through horizontal distance x0 in a time of T/4 I write x0 = 1/2 . g.tan(θ) . (T/4)2 (assuming the initial speed is zero) and find that T = √[32x0/g.tan(θ)] = 4√[2x0 / g.tan(θ)] I would like to know if this is correct. It seems like it should be the sort of thing you could just look up, but I don't seem to be able to describe the system well enough to Google to get results about anything other than harmonic oscillators.