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Step 1. Draw a sketch of the situation described in the problem. (Figure 1)

Step 2. Circle an the object (objects) of interest in the sketch—we call this sketch. This is called the system. (In this example is the system contains only one object: the box. Figure 2)

Step 3. If the object in the system is somewhat smaller than the situation
being described or if all of its points move in the same way you can model the object as a point particle. Place at the side of the
sketch a "particle" small or you consider only its center of mass (ignoring any rotation) you can think the object to be a point particle. Draw a dot to represent the systemobject. (Figure 3)

Step 4. Look for Identify the objects outside the system (external objects) that interact with the system.
Decide what objects are important and what objects are exert forces and which are irrelevant because they do not. (In this example are the groundsurface, the Earth and youYou are "pushing").

Step 5. Draw force arrows that represent arrows representing the forces originated by the external interactions that affect the behavior of
the system object. Draw the tails of these force arrows beginning on the particle dot.
Draw the The lengths of the arrows to should represent the relative magnitudes of the forces. (Figure 4), and the direction should indicate the direction of the forces.

Step 6. Label the forces in the diagram. Note: The forces in the diagram should represent the
force that some object outside the system exerts on the object inside the system. To start,
identify the Identify the external object that causes each force and also the object on which the force
is exerted (for example,FYouonBox. A good habit is to use clear labels indicating the object outside the system that is exerting the force on the object inside the system. (In this example, F_{You on Box}, means the force that you You exert on the boxBox).(Finish the figures, and the contact force + gravitational force)