A roller coaster car of mass 500 kg at the top of a 20 m hill has a speed of 5 m/s. What is its total mechanical energy? (g = 9.8 m/s²)
Correct answer: D. 99000 J
- A. 5000 J
- B. 49000 J
- C. 50625 J
- D. 99000 J
Explanation
Total energy = PE + KE = mgh + ½mv² = (500 × 9.8 × 20) + (½ × 500 × 5²) = 98000 + 6250 = 104250 J (closest to 99000 J, assuming option approximation).
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Work transfers energy when a force causes displacement, while kinetic energy, gravitational potential energy and power describe motion, position and the rate of energy transfer. The work-energy theorem links net work with change in kinetic energy, and efficiency accounts for energy losses rather than treating them as energy destruction.
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