InterviewSolution
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InterviewSolution
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A ball is thrown upwards . Its height varies with time as shown in figure. If the acceleration due to gravity is `7.5 m//s^(2)`, then the height h is A. 10mB. 15mC. 20mD. 25m |
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Answer» Correct Answer - B The height h is convred in time interval t=1s to t =2s or t=5s to t=6s. Let u be the initial velocity given to the ball when projected vertically upwards. Then `h=s_(2)-s_(1)=s_(5)-s_(6)` .....(i) `s_(2)-s_(1)=(uxx2-(1)/(2)xx7.5xx2^(2))-(uxx1-(1)/(2)xx7.5xx1^(2))` `=u-(3)/(2)xx7.5` .....(ii) `s_(5)-s_(6)=(uxx5-(1)/(2)xx7.5xx5^(2))-(uxx6-(1)/(2)xx7.5xx6^(2))` `=-u+(11)/(2)xx7.5` `therefore u-(3)/(2)xx7.5=-u+(11)/(2)xx7.5` or `2u=(14)/(2)xx7.57xx7.5` or `2u=(14)/(2)xx7.5=7xx7.5` or `u=7xx(7.5)/(2)=26.25 m//s` `therefore h=26.25-(3)/(2)xx7.5=26.25-11.25=15.0m` |
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