Terminal velocity of falling raindrop

Steps:

• Graph shows speed increasing over time then becoming constant.
• Constant speed means acceleration is zero.
• Acceleration equals resultant force divided by mass (Newton's second law).
• Resultant force is weight minus increasing air resistance, which rises with speed until balancing weight.

Why A is correct:

• Newton's second law states acceleration equals net force over mass; as air resistance grows, net force shrinks, reducing acceleration to zero and yielding steady speed.

Why the others are wrong:

• B: Air resistance increases with speed due to greater opposition to motion.
• C: Resultant force decreases toward zero as air resistance rises.
• D: Resultant force does decrease, but acceleration's drop to zero directly causes the steady speed.

Final answer: A