posted by dave .
In February 1955, a paratrooper fell 365 m from an airplane without being able to open his chute but happened to land in snow, suffering only minor injuries. Assume that his speed at impact was 60 m/s (terminal speed), that his mass (including gear) was 90 kg, and that the force on him from the snow was at the survivable limit of 120000 N. What are (a) the minimum depth of snow that would have stopped him safely and (b) the magnitude of the impulse on him from the snow?
(b) The impulse the snow had to exert on him equaled the momentuum of him and his gear at impact:
M*V = 90 kg*60 m/s = 5400 kg m/s
(a) For the mimimum snow depth needed to avoid a lethal force greater than 120,000N
Kinetic energy @ impact = 120,000*depth
= (1/2)*90*65^2 = 190,000 J
Depth = 190,000/120,000 = 1.6 meters