a skydiver is subject to two forces: gravity and air resistance. Falling vertically, she reaches a constant terminal speed at some time after jumping from the plane. Since she is moving at a constant velocity from that time until her chute opens, we conclude from the work kinetic energy theorem that, over that time interval,

A. The work done by gravity equals the negative of the work done by the air resistance.
B. The work done by gravity is zero.
C. The work done by gravity equals the work done by air resistance.
D. The work done by air resistance is 0.
E. Her kinetic energy increases.

Please help me with this...

Duplicate post. See answer given to later post of same question.

To determine the correct answer, let's analyze the concept behind the work-energy theorem.

The work-energy theorem states that the work done on an object is equal to the change in its kinetic energy. Mathematically, this can be expressed as:

Work = Change in Kinetic Energy

In the case of the skydiver falling vertically, two forces are acting on her: gravity and air resistance. The force of gravity is directed downward, while the force of air resistance opposes the motion and is directed upward.

When the skydiver jumps out of the plane, initially, gravity is the dominant force, and she accelerates due to the gravitational pull. As she continues to fall and her speed increases, air resistance gradually becomes stronger until it equals the force of gravity. At this point, the skydiver reaches terminal velocity, where the upward force exerted by air resistance equals the downward force exerted by gravity. As a result, the skydiver experiences no further acceleration and moves at a constant velocity.

At terminal velocity, the net force acting on the skydiver is zero, meaning the work done on her by both gravity and air resistance is zero. Since work done is zero, there is no change in kinetic energy. Therefore, we can conclude that the correct answer is:

B. The work done by gravity is zero.

This is because when the skydiver reaches terminal velocity and continues to fall at a constant velocity until her chute opens, the work done by both gravity and air resistance is zero.