If you put something like a piece of cardboard between a magnet and an iron nail the magnets to hold the nail in place even though the magnet is not touching the nail explain how that happens

The astronauts on the space shuttle flights experienced an acceleration of 29 m/s2 (about 3 "g's") during lift-off. what upward force must the astronaut's seat apply to the astronaut in order to cause this acceleration? assume the astronaut's mass is 70 kg, and compute this force when the acceleration is near the earth's surface so their weight equals latex: mg m g .