John has a body mass of 90 kg and walks on three different surfaces. At heel strike the ground

reaction force Fg,x is 170 N. Would he slip on (1) ice surface, (2) loose gravel, and (3) concrete? Given

that s is 0.1 for shoe-ice, 0.2 for shoe-loose gravel, and 0.7 for shoe-concrete. If he slips on any

surfaces, list two suggestions that you would give him to prevent the slip.