Q

A roller coaster car of mass 500 kg moves down a steep track, converting its potential energy into kinetic energy. At the lowest point, it is moving at 20 m/s. If the car encounters a section with friction that removes 30,000 J of energy, what is its new speed, assuming no other forces act?

RRB Group D 13 Aug, 2026 (12:45 PM - 2:15 PM) 2026
✓ Answer: C ≊18 m/s
Initial kinetic energy is ½mv² = ½×500×20² = 100,000 J. After 30,000 J is lost, 70,000 J remains, giving v = √(2K/m) ≈ 16.7 m/s, closest to 18 m/s.
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