The skater produces a pressure of 500 kPa on the ice. Find the mass of the skater if the skates are 40 cm long and 3 mm wide.

Let’s calculate the area of the skate blade:
0.4 * 0.003 = 1.2 10 ^ -3 m ^ 2,
then the area of the two blades is:
2 * 1.2 * 10 ^ -3 = 2.24 * 10 ^ -3 m ^ 2
Since, by definition, the pressure is P = m * g / S where m is the mass, S is the surface area, g is the acceleration of gravity, then
m = P * S / g = 500 * 10 ^ 3 * 2.24 * 10 ^ -3 / 10 = 112 kg.