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42. An aeroplane is flying at a height of 1960 m inhorizontal direction with a velocity of 360 km/hr.When it is vertically above the point A on theground, it drops a bomb. The bomb strikes a pointB on the ground, then the time taken by the bombto reach the ground is-(1) 2012 sec(2) 20 sec(3) 10.2sec(4) 10 sec |
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Answer» Answer: 20 s Explanation: Along vertical direction Initial velocity of bomb = 0 m/s Height from which it is dropped = 1960 m Then, from equation of MOTION, s = UT + 0.5at² 1960 m = (0 m/s × t) + (0.5 × 9.8 m/s² × t²) t² = 1960 m / (4.9 m/s²) t = sqrt(1960/4.9) s t = sqrt(400) s t = 20 s |
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