Friction

Background Information:

The Physics:

Static friction is defined by the inequality F_s ≤ μ_sN. The figure above illustrates the forces that act on an object being pushed up an inclined plane. We can visualize the normal force N (vector pointing up perpendicular to the plane), the user-applied force F (pointing right), static friction F_s (pointing in the opposite direction of F in this case), and the force of gravity G.

Traditional Learning Methods:

The fact that the static frictional force is described by an inequality is the ultimate source of difficulty for many students. Since all forces they have seen before are described by ordinary equalities, they tend to set F_s = F_smax. Depending on the problem, students may not be able to realize their mistake. If the force applied to an object is less than F_smax, the use of the incorrect equality F_s = F_smax yields a nonphysical result. This dynamic component is necessary to understand this phenomenon, however, it cannot be adequately illustrated in a textbook.

Motivation:

When developing visuo-haptic simulators, we look for concepts that involve forces in order to present them from a novel perspective. We chose friction since we observed that students have difficulty applying the theoretical concepts to problems. To provide a different perspective on the forces that act on a block on an inclined plane, we developed a 3D visuo-haptic simulator.

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