In which of the following situations would a person most likely NOT feel weightless?
(a) A passenger inside an elevator whose supporting cable has just broken and allowed the car to fall freely
(b) An astronaut orbiting Earth inside a spacecraft moving at constant speed in a circular path
(c) A skydiver descending at terminal speed before her parachute opens, with air resistance equal in magnitude to her weight
(d) A roller-coaster rider passing over the top of a hill at just the right speed so that the normal force becomes zero