Free-body diagrams are graphical representations of various forces on an object. This can be understood with some examples. The free-body diagram for a lamp hanging from a chain can be shown as a point with two forces: the gravitational force and the tension in the chain. Taking another example, sketch a free-body diagram for a cart carrying a large box. Here, there are two systems of interest, the box and the cart; thus, there is a need to draw separate diagrams for each. The forces acting on the box are the gravitational force due to its mass, the normal force, and the frictional force exerted by the cart on the box. For the cart, the gravitational force, the net normal force due to the ground, a normal force due to the box on the cart, the net frictional force exerted by the ground and the box on the cart, and a push that is applied on the handle, all act together.