A particle of mass m is inside a long, narrow tube which rotates a constant angular velocity ω in the horizontal plane. (This means that you see the tube from the top of the figure and not from the side.) At time t = 0 is the particle on the radial distance a from the rotational axis and the radial velocity is zero. Then begins the slide without friction. Determine the particle radial distance from the rotation axis and the horizontal normal force of the particle from the tube functions of the time! Why is equation (10) found in this solution https://dl.dropboxusercontent.com/u/12645136/Losningar.pdf [Broken] equal to 0? If the particle moves from the center outwards isn't a force acting upon it in the radial direction? Hence giving it an acceleration in the same direction?