The Free-Body Diagrams for Inclined Planes Concept Builder requires that you identify all types of forces acting upon a box moving along an inclined plane. You must identify both the type and the direction of the forces.

Identifying the type of force can be difficult since Physics teachers will often use different names to describe the same type of push or pull that is exerted on an object. For instance, one teacher's drag force is another teacher's air resistance force. And one teacher's thrust force is another teacher's applied force. So to help with such ambiguities, we have prepared a page of defintions that The Physics Classroom uses to describe the force types. Use these definitions in answering the questions of this Concept Builder.

 

Force Types

Gravity Force: Gravity falls into the category of a non-contact force. It is the result of the interaction between two masses. All objects with mass attract. And when the Earth or some other very massive object is present, the gravity force is significant in size. For an object on Earth, you can always count on this force being present. Earth's gravity always pulls objects straight downward.

Normal Force: A normal force exists whenever two surfaces are pressed against one another.  Sit on a chair, stand on the floor, lean against the wall ... in all cases your body and another surface are pressing against each other. This pressing together results in a force on your body (and on the object). This is called a normal force. A normal force is always directed perpendicular (at right angles) to the surface.

Applied Force:  This force is the result of person pushing or pulling on an object. A careful reading of the description of the situation will often describe a person "applying a force." This force could be considered a sub-type of the normal force. For our purposes, we will think of the applied force resulting when another person is doing the pushing or pulling on the object. The direction of the applied force is in the directioni that the person is pushing or pulling.

Tension Force: Tension is the force that results when a rope, string, cable, or wire is attached to an object and exerting a push or pull on the object. Read the description of the situation carefully and look for words that describe a rope, wire, string, or cable pulling on the object. A tension force is alway directed from the object along the rope's line towards the person or thing that holds the opposite end.

Friction Force: Friction force results when two touching surfaces are sliding across each other (sliding friction) or attempting to slide across each other (static friction). Read the problem carefully to determine if the object's surface is in contact with another surface. Then determine if the object is moving across the surface; if it is, then there is a sliding friction force. The sliding friction force is always directed iopposite of the direction the object is moving.


Of course there are other forces; but the ones described above are the ones you will be using in this Concept Builder.