A skydiver jumps out of an airplane and begins to fall. Even before opening his parachute, he encounters air resistance, a friction - like force. Eventually, he stops accelerating. During his fall, his total mechanical energy is alwaysover time?

I think so but yes the skydiver experiences this resistance and this sudden grab of air because of the air being caught by the parachute will be like a car's brake system it will capture all that falling energy and air energy and grabbing it all to cause a sudden grab the reason he starts to slow down is the shape of the parachute. the parachute is still grabbing all the air making a little air ballon mechanism pretty much. have you ever put your hand out of a car window and made it flat to where the wind hits the whole hand and your hand is grabbed back? that is the reason i just explained