1.

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

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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