The wheel & rolling
- Place a Christmas star on the table. Push it forward. It “rolls” a few “steps”. The spike that touches the table didn’t slide – the contact point was fixed and still – the rest of the star just “fell forward” over this contact point.
- Now add more spikes and repeat. Again, the contact point stays still. No sliding, only “falling forwards”.
- Now add more and more spikes – until there are so many that the star is basically round – and repeat. Each point on this round periphery represents a spike. So, each point stays still when in contact.1
- ‘Sears and Zemansky’s Univesity Physics with Modern Physics’ (book), Hugh D. Young & Roger A. Freedman, Pearson Education, 13th ed., 2012
- ‘Wheels’ (web page), Chris Woodford, Explain That Stuff!, 2018, www.explainthatstuff.com/howwheelswork.html (accessed Feb. 7th, 2020)