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From the top of a tower 40 m high a ball is projected upwards with a speed of 20 ms -1 at an angle 30° with the horizontal. The ratio of the total time of flight to hit the ground to the time taken by it to come back to the same initial elevation (g = 10 ms^(-2) ) is : |
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Answer» `3:2` `T=(2usintheta)/g=(2xx20xx1/2)/10=2`sec Time taken to GO from C to D is `h=ut + 1/2g t^(2)`, INITIAL vertical velocity= `20sin30^@` `40=20xx1/2xxt +5t^(2)` `implies t^(2)+4t -2t-8=0` r(t + 4)-2(t + 4) = 0 (r + 4) (r-2) = 0 `implies` t = 2 s as time cannot be negative.  `:.` Time taken to go from A to D= 2+2=4s `:.` ratio of timings = `4/2=2:1` |
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