Net work by forces increases kinetic energy over distance

Steps:

• Calculate net upward force: engine force (3.5 MN) minus weight (1.9 MN) minus air resistance (0.1 MN) = 1.5 MN.
• Convert to newtons: 1.5 MN = 1.5 × 10^6 N.
• Compute work by net force over 100 m: (1.5 × 10^6 N) × 100 m = 1.5 × 10^8 J.
• Convert to MJ: 1.5 × 10^8 J = 150 MJ; this equals the increase in kinetic energy.

Why A is correct:

• Work-energy theorem states net work done on the rocket equals its change in kinetic energy.

Why the others are wrong:

• B: 170 J is orders of magnitude too small, ignoring MN scale and distance.
• C: 350 MJ uses only engine force work, ignoring opposing forces.
• D: 550 MJ adds engine and weight magnitudes incorrectly, not net force.

Final answer: A