A 40-kg skater is standing still in front of a wall. By pushing against the wall she propels herself backward with a velocity of -1 m/s. Her hands are in contact with the wall for 0.80 s. Ignore friction and wind resistance. Find the magnitude and direction of the average force she exerts on the wall (which has the same magnitude, but opposite direction, as the force that the wall applies to her). magnitude N direction