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3) constant(4) none of theseA stone weighing 3 kg falls from the top of a tower 100 m high and buries itself 2 m deep in the sand.The time of penetration is(1) 0.09 sec(2) 0.9 sec(3) 2.1 sec(4) 1.3 sec |
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Answer» Given :m = 3 kg u = 0h = 100 mg = 9.8 m/s² Using 3rd equation of motion :v² - u² = 2gh v² - 0² = 2 (9.8) 100v = 2√490 v = 14√10 m/s Now, during penetration :u = 14√10 m/sv = 0S = 2 ma = ?t = ? Using 3rd equation of motion; v² - u² = 2aS 0² - (14√10)² = (2) a (2)4a = -1960a = -490 m/s² Now, using 1st equation is motion ;v = u+at0 = 14√10 + (-490)tt = 14√10/490t = 0.0903 sec (1) is correct option |
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