Unbalanced gravitational force causes acceleration

Steps:

• Gravity acts downward on the apple with force mg.
• Air resistance is negligible initially, so net force is unbalanced.
• Newton's second law (F = ma) gives constant acceleration a = g ≈ 9.8 m/s².
• Velocity increases linearly, not at constant speed.

Why B is correct:

• Unbalanced net force (gravity dominant) results in constant acceleration, as per F_net = ma with constant g.

Why the others are wrong:

• A: Forces are unbalanced due to gravity, causing acceleration, not constant speed.
• C: Unbalanced forces produce acceleration, not constant speed (which requires balance at terminal velocity, but not during initial fall).
• D: Identical to C; unbalanced forces do not yield constant speed.

Final answer: B