You encounter a 4.3 m long stretched string that is clamped at both ends. You launch a pulse from one end that returns in 0.37 s. What is the frequency of the 3rd normal mode in Hz?

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.