A girl pushes a box across a desk. The girl does not move, but the box moves at a constant speed to the right. Classify the following as either forces on the girl or forces on the box or both. Static Friction
Sliding Friction
Push to the right
Push to the left
Air resistance

Forces on the Grid:

Forces on the Box:

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.