A thin, homogeneous bar of length *L* is support by a smooth sliding joint at the top end A. With the bar initially at rest, a force *F* is applied a distance of d below A. What is the instantaneous acceleration of end A as a result of the applied force?

From the above, we see that:

- When d/L = 1/2 (force applied at the center of mass G), the acceleration of A is
*a*_{A}=*F/m.*This is expected since in this case the bar is in pure translation. - When d/L = 2/3, the acceleration of A is
*a*_{A}=*0.*The location of the applied force in this case is known as the "center of percussion" (or, "sweet spot"); that is, no force is required at end A in order to keep A stationary at the instant that the force is applied.

An animation of the simulation for this problem is shown for four values of the application point *d*. For d/L > 2/3, the acceleration of end A is initially to the left for a force applied to the right on the bar.