Dear All, Suppose we have a movable inclined plane (initially at rest) which has height h (if we attach wheels, then it should be movable) and assume that there is no friction anywhere. If a block travels with speed V towards the plane and goes up to the distance h, I wonder ; Is mechanical energy of the block alone is conserved ? (not kinetic energy!) First of all, I would like to know whether it is a collision or not. If the block is going through the plane, are they colliding ? And if they are colliding, then it certainly is not an elastic collision. So total kinetic energy must not be conserved. But would equation mblock * g * hblock = 1/2 mblock * Vinitial^2 - 1/2 mblock * Vfinal^2 hold ? (I thought I could use conservation of momentum to calculate Vfinal ) PS: I didn't want to post it as homework question to the other forum because it isn't a homework, only a conceptual exercise that I have imagined but have been unable to come up with a reasoning.