Tippe Top (Aluminum)
This spinning top has a surprising behavior. When spun, it will introvert itself to spin upside down until it loses momentum. This interesting gyroscopic effect is generally credited to surface friction. This small friction causes a torque which gradually rotates the sphere on a second axis and forces it up onto the stem. Note the direction of rotation before and after it flips.
This precision tippe top was machined from aluminum to achieve the best effect. Also available in painted wood.
Tippe tops (also known as flip over tops) were originally invented in 1950 by the Danish engineer Werner Ostberg. His inspiration came from a visit to South America where he had seen local people playing with a small round fruit. When they turned it by the stalk like an old-fashioned spinning top, it would spin for a second and then invert and spin on the stalk. (Pictured: Bohr and Pauli investigating a tippe top).
Diameter: 29mm (1.14")
Hieght: 36mm (1.41")
A tippe top usually has a body shaped like a truncated sphere, with a short narrow stem attached perpendicular to the center of the flat circular surface of truncation. The stem may be used as a handle to pick up the top, and is also used to spin the top into motion. When a tippe top is spun at a high angular velocity, its stem slowly tilts downwards more and more until it suddenly lifts the body of the spinning top off the ground, with the stem now pointing downward. Eventually, as the top's spinning rate slows, it loses stability and eventually topples over, like an ordinary top.
At first glance the top's inversion may mistakenly seem to be a situation where the object spontaneously gains overall energy. This is because the inversion of the top raises the object's center of mass, which means the potential energy has in fact increased. What causes the inversion (and the increase in potential energy) is a torque due to surface friction, which also decreases the kinetic energy of the top, so the total energy does not actually increase. Once the top is spinning on its stem, it does not spin in the opposite direction to which its spin was initiated. For example, if the top was spun clockwise, as soon as it is on its stem, it will be spinning clockwise viewed from above. This constant spin direction is due to conservation of angular momentum.