Final answer:
A parachute can't reduce a skydiver's speed to zero because the forces of gravity and air resistance reach a dynamic equilibrium, leading to a non-zero terminal velocity.
Step-by-step explanation:
Opening a parachute cannot reduce the speed of a skydiver to zero because even with the parachute open, the skydiver continues to be subject to the gravitational force pulling them downwards. While the parachute significantly increases air resistance (drag) and reduces the terminal velocity of the skydiver, it does not eliminate the force of gravity. As a result, the skydiver descends at a reduced, but non-zero, terminal velocity until they reach the ground. The key factors at play are the forces of gravity and air resistance, working against each other to achieve a state of dynamic equilibrium where they are almost equal, thereby allowing the skydiver to fall at a constant velocity rather than continue accelerating.
When a skydiver falls, they reach a terminal velocity, which is the maximum speed they can achieve due to the balance between the gravitational force pulling them down and the air resistance pushing against them. The parachute opens up a large surface area, which increases the air resistance and slows down the skydiver, but it does not instantly reduce their speed to zero.
Instead, the parachute gradually slows down the skydiver by increasing the time it takes for them to reach the ground. This is because the parachute creates more air resistance, causing the skydiver to decelerate and fall at a slower speed.