Acceleration decreases due to air resistance

Steps:

• Object starts with zero velocity, so initial air resistance is zero; net acceleration equals g = 9.8 m/s² downward.
• As speed increases, air resistance (drag force) grows proportional to velocity squared.
• Net force = mg - drag; thus, net acceleration = g - (drag/m), which decreases over time.
• At terminal velocity, drag = mg, so acceleration reaches zero.

Why C is correct:

• Newton's second law shows net acceleration decreases to zero when opposing forces balance at terminal velocity.

Why the others are wrong:

• A: Acceleration starts at 9.8 m/s² and decreases, not the reverse.
• B: It begins at 9.8 m/s² and decreases, so does not increase to that value.
• D: Air resistance causes acceleration to vary, not stay constant.

Final answer: C