Roller Top

‘Roller top’ is a spinning top that has two sets of wheels located around its circumference.

The basic physical principle of this toy is angular momentum.  When the top loses enough angular momentum, it falls on its side.  The top continues to spin on its side wheels, however, until its angular momentum equals zero. 

Children interact with ‘roller top’ by first ‘spinning’ or ‘revving up’ the top by spinning it on its shaft.  The child then places the top (tip down) on a flat surface, and the top spins freely on the surface.  After that, the child observes how the top continues to spin even after it falls on its side. Finally, the toy is fun because it spins according to the speed with which the child revs it up. Thus, the child has lots of control over the toy's behavior.

The construction cost of this toy is approximately $2.00.  This construction cost is equally split between the cost of the top’s material (plastic) and the cost of constructing two sets of wheels around the toy.  Furthermore, the top is made of plastic, and the wheel are tightly fastened to the plastic with shielded bearings for extra protection. So, the toy is appropriate for use on smooth surfaces, but it may wear if it is used on rougher surfaces.  Lastly, there are no small parts that can come easily undone on this toy.  Thus, the toy is meant for children 2 years of age and older.