Aworld-class sprinter can reach a top speed of about 11.5 m/s in the first 18.0 m of a race. what is the average acceleration of this sprinter and how long does it take him/her to reach that speed?

Two steel balls, each of mass m, are welded to a light rod of length l and negligible mass and are initially at rest on a smooth horizontal surface. a horizontal force of magnitude f is suddenly applied to the rod as shown. determine (a) the instantaneous acceleration a of the mass center g and (b) the corresponding rate at which the angular velocity of the assembly about g is changing with time.