Three foot positions of the human gait (heel strike, midstance, and toe-off) are shown below.[br][br]For each of the foot positions, two forces will act on the foot-ground system. One acts on the foot, called the Ground Reaction Force (GRF). The other is equal and opposite and magnitude (as per Newton's third law) and acts on the ground.[br][br]For the simulation below, drag the tails of each of the six red vectors to the appropriate foot-ground system. Forces acting on the foot should go on the upper green dots. Forces acting on the ground should go on top of the lower green dots.[br][br]Click submit to see which of these vectors are in the correct location, and click reset to move all vectors back to their original positions.

Created by Lewis Hicks and Priya Jamkhedkar for the Portland State University Physics Department, 2021.