Vertical GRFs are directed how relative to the surface?

Vertical GRFs are directed how relative to the surface?

• A. Parallel
• B. Diagonal
• C. Medial-lateral only
• D. Perpendicular

Answer: (D)

Vertical ground reaction forces come from the contact with the surface and act normal to that surface. The surface resists perpendicular deformation, so the reaction is directed perpendicular to the interface, pushing upward away from the surface to support the body’s weight. Horizontal forces can exist due to friction, but the vertical component specifically is perpendicular to the surface.

Vertical ground reaction forces come from the contact with the surface and act normal to that surface. The surface resists perpendicular deformation, so the reaction is directed perpendicular to the interface, pushing upward away from the surface to support the body’s weight. Horizontal forces can exist due to friction, but the vertical component specifically is perpendicular to the surface.