Newton's Second Law: Driving Force Overcomes Friction for Acceleration

Steps:

• Calculate net force: F_net = m × a = 800 kg × 2.5 m/s² = 2000 N forward.
• Frictional force acts backward: 1200 N.
• Driving force F_d minus friction equals net force: F_d - 1200 N = 2000 N.
• Solve for F_d: F_d = 2000 N + 1200 N = 3200 N.

Why D is correct:

• Driving force provides both the net force for acceleration (ma) and counters friction, so F_d = ma + f_friction = 3200 N, per Newton's second law (ΣF = ma).

Why the others are wrong:

• A: 800 N equals mass alone, not a force calculation.
• B: 1200 N is just friction, neglecting acceleration force.
• C: 2000 N is net force (ma), but excludes friction to be overcome.

Final answer: D