Throw a frees-bee. It flies at some speed $v$. But exactly what is moving at that speed $v$? It spins while flying, so each “particle” it is made of moves at different speeds.1 Except for the centre! That point moves at the speed $v$.
But then throw a hammer. What is its “centre”? Which point is moving at the thrown speed $v$? Which point is the hammer itself spinning about?
- ‘Center of mass of System of particles’ (web page), Physics Catalyst, 2016, www.physicscatalyst.com/mech/center-of-mass.php (accessed Feb. 10th, 2020)
- ‘Sears and Zemansky’s Univesity Physics with Modern Physics’ (book), Hugh D. Young & Roger A. Freedman, Pearson Education, 13th ed., 2012