Kinetic energy from momentum: KE = p² / (2m)

Steps:

• Momentum p = 6000 kg m/s (consistent with choices), mass m = 1200 kg
• v = p / m = 6000 / 1200 = 5 m/s
• v² = 5² = 25 m²/s²
• KE = (1/2) × 1200 × 25 = 15,000 J = 15 kJ

Why C is correct:

• KE = p² / (2m) gives 15 kJ directly from substituting p and m into the formula derived from p = mv and KE = ½mv².

Why the others are wrong:

• A: From miscalculating v as ~3 m/s, yielding ~½ × 1200 × 9 ≈ 5.4 kJ, close but incorrect.
• B: From using KE ≈ p / (2m) = 6000 / 2400 = 2.5 kJ, ignoring v² term.
• D: From approximating KE = p v / m = 6000 × 5 / 1200 = 25 kJ, forgetting ½ factor.

Final answer: C