A 40 kg block is resting at a height of 5 m off the ground. If the block is released and falls to the ground. Which of the following is closest to its total mechanical energy at a height of 2m, assuming negligible air resistance?
Correct answer: D. 2000J
- A. 0 J
- B. 400 J
- C. 800 J
- D. 2000J
Explanation
The total mechanical energy of the block at any point during its fall is the sum of its potential energy (PE) and kinetic energy (KE). Initially, at 5m, the block has only potential energy calculated by PE = mgh = 40 kg × 9.8 m/s² × 5 m = 1960 J. As it falls, its potential energy decreases, and kinetic energy increases, but the total mechanical energy remains constant, assuming negligible air resistance. Therefore, at 2m, the total mechanical energy is still approximately 2000 J, making Option D correct.
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