Which piece of lab equipment would be least useful in finding the precise density of an unknown liquid?
a. beaker
b. graduated cylinder c. electronic balance
d. triple-beam balance

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.