Free fall from rest: v² = 2gh

Steps:

• Initial velocity u = 0 m/s since dropped from rest.
• Final velocity v = 14 m/s at ground; acceleration g = 10 m/s² (negligible air resistance).
• Apply kinematic equation: v² = u² + 2gh → 14² = 2(10)h.
• Solve: 196 = 20h → h = 9.8 m ≈ 10 m.

Why B is correct:

• Kinematic equation v² = 2gh directly yields h = v²/(2g) = 196/20 = 9.8 m, matching 10 m under standard g approximation.

Why the others are wrong:

• A: Gives v = √(2×10×2) ≈ 6.3 m/s, far below 14 m/s.
• C: Gives v = √(2×10×20) = 20 m/s, exceeding 14 m/s.
• D: Gives v = √(2×10×40) ≈ 28.3 m/s, much higher than 14 m/s.

Final answer: B