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An object is released from rest and falls freely under gravity. It is observed to be 400 m above a point P, 4 s before it reaches P. Taking g = 10 m/s², from what height above P was the object dropped?
- 720 m
- 900 m
- 320 m
- 680 m
Correct answer: 720 m
Solution
The object falls freely under gravity, and after 4 seconds, it has fallen a distance of 80 m (using the formula d = 0.5 * g * t²). Since it is 400 m above point P at that time, the total height from which it was dropped is 400 m + 80 m, equaling 480 m. However, the total distance fallen from the original height to point P is 720 m, accounting for the entire fall.
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