A 50kg gymnast lands vertically from rest after dropping 2.0m onto a foam pad. To limit the magnitude of the average force exerted on her body to 1.5×104N, what minimum pad thickness (assume uniform deceleration within the pad) is required? (Take g=9.8m s−2.)
a) about 13.5cm
b) about 6.5cm
c) about 3.4cm
d) about 65cm