Falling Safely

Terminal Speed

When a skydiver jumps out of an aeroplane, the speed of his descent can be considered in two separate parts:

• before the parachute opens (when the skydiver is in freefall)
• after the parachute opens (when air resistance is greatly increased)

BEFORE THE PARACHUTE OPENS:

• When the skydiver jumps, he initially accelerates due to the force of GRAVITY
• As he falls, he experiences the FRICTIONAL FORCE OF AIR RESISTANCE in the opposite direction. At this point, WEIGHT is greater than the frictional force of air resistance, so he continues to accelerate.
• As his speed increases, so does the AIR RESISTANCE acting on him.
• AIR RESISTANCE increases until it's equal to WEIGHT. The resultant force now acting on him is zero and his falling speed becomes CONSTANT as forces are BALANCED. This speed is called the TERMINAL SPEED.

AFTER THE PARACHUTE OPENS:

• When the parachute is opened, unbalanced forces act again because the UPWARD FORCE OF AIR RESISTANCE is greatly increased and is bigger than WEIGHT.
• The increase in the FRICTIONAL FORCE…