a person falls flat on their back on some slipper ice and is unconscious for a second. the horizontal position of their legs, torso and head from their feet is given by 0.48m, 1.35m and 1.7m respectively and their weights are 30kg, 50kg and 10kg. they try to sit up on the ice which is so slippery that they are not able to move their horizontal centre of mass. the new positions of their legs, torso and head from their feet are 0.16m, 0.52m, and 0.72m. what is the change in position of the person's feet?