Work-energy theorem applies

Steps:

• Initial KE = (1/2) * 60 kg * (3 m/s)^2 = 270 J
• Final KE = 0 J (at rest)
• Change in KE = -270 J; work against braking = 270 J (magnitude)
• Work = force * distance, so force = 270 J / 5.0 m = 54 N

Why C is correct:

• Braking force equals change in KE divided by distance, per work-energy theorem.

Why the others are wrong:

• A: 18 N assumes distance of 15 m instead of 5 m.
• B: 27 N uses half the KE change (135 J).
• D: 108 N doubles the initial velocity to 6 m/s.

Final answer: C