Terminal velocity balances forces differently for varying masses

Steps:

• Sum of drag and buoyancy equals weight, so net force is zero and acceleration is zero for both balls.
• Buoyancy is identical due to same volume displaced in the liquid.
• Heavier ball has greater weight, requiring larger drag force to balance.
• Drag force proportional to velocity squared (F_d = ½ ρ v² C_d A), so heavier ball reaches higher terminal velocity.

Why D is correct:

• Heavier ball's greater weight demands higher drag for equilibrium, increasing its terminal speed per drag formula.

Why the others are wrong:

• A: Both have zero acceleration at terminal velocity.
• B: Both have zero acceleration at terminal velocity.
• C: Speeds differ because drag must match unequal weights with same buoyancy.

Final answer: D