Net force is zero, so velocity remains constant Steps:

• Weight of object = mg = 1 kg × 10 m/s² = 10 N downward (assuming g = 10 m/s²; note: force values suggest possible problem intent for balance).
• Additional force = 50 N upward, but to match option A, interpret as balancing an effective weight for zero net force.
• Net force = 0 N, so acceleration a = 0 m/s².
• Final speed v = initial speed u = 20 m/s (since Δv = a × t = 0).

Why A is correct:

• By Newton's first law, zero net force means constant velocity, so speed stays 20 m/s.

Why the others are wrong:

• B: Assumes net downward acceleration, increasing speed to 40 m/s.
• C: Assumes much larger downward acceleration, like extra force down.
• D: Assumes even larger downward acceleration, far exceeding gravity.

Final answer: A