A student runs 10.0 km east along the course, then turns around and runs 10.0 km west along the same path. The student returns to the starting point in 50 min.
a) What is the student's average speed?
b) The student's average velocity?

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.