WAEC 2016 Physics · Question 28

A ball is dropped from the top of a tower. Due to air resistance,it reaches terminal velocity. Which of the…

Question

A ball is dropped from the top of a tower. Due to air resistance,it reaches terminal velocity. Which of the following statement(s) about its motion is/are correct? i. The acceleration of the ball is zero. ii. The net force on the ball is zero. iii. The velocity of the ball increases.

A.i only
B.i and ii only
C.ii and iii only
D.i, ii and iii

Answer: B. i and ii only

Explanation written with AI and checked against the answer key

Analyze the question: The ball has reached terminal velocity. We need to decide which of the three statements describe its motion at that stage.

Concept: Terminal velocity is reached when the upward air resistance (drag) grows until it equals the downward weight of the ball.

Weight (downward) = Air resistance (upward)
Net force F = mg − R = 0
By Newton's second law, F = ma, so a = 0
With zero acceleration, the velocity stays constant, and the ball falls at a steady speed.

Checking each statement:

i. The acceleration of the ball is zero. Correct. Net force is zero, so a = 0.
ii. The net force on the ball is zero. Correct. Weight is balanced by air resistance.
iii. The velocity of the ball increases. Incorrect. The velocity is constant at terminal velocity. It increased earlier in the fall, but it no longer does.

So only statements i and ii are correct.

Answer: B. i and ii only.

Exam tip: Whenever you see "terminal velocity", remember: forces balanced → a = 0 → constant velocity. Any option claiming that speed is still increasing at terminal velocity is wrong.

AI can make mistakes. Report anything that looks wrong.