Final answer:
A hard opening is a malfunction on a personnel parachute caused by excessive opening forces, which can occur when a parachute departs too quickly, leading to potential injury .
Step-by-step explanation:
The malfunction on the personnel parachute caused by excessive opening forces is typically called a hard opening. This occurs when the parachute opens too quickly and the deceleration is so abrupt that it can cause injury to the parachutist or damage the parachute equipment. When a skydiver reaches terminal velocity, which is about 200 km/h in a spread-eagle position and can be up to 350 km/h in a headfirst position, the opening of the parachute drastically reduces this velocity. The resulting force can be quite significant, as it involves converting the skydiver's potential energy into kinetic energy and then quickly dissipating this kinetic energy when the parachute opens.
Excessive opening forces can be compared to the forces experienced during explosive seat ejection from an aircraft, though ejection forces are designed to be survivable. In contrast, parachute openings should be less severe. If a parachute deploys too rapidly, the immense forces exerted on both the jumper and the gear can lead to fractures or equipment failure, akin to the high forces exerted on one's legs when landing stiff-legged from a jump without rolling to dissipate the force over a longer period.