A bullet travelling horizontally looses `1//20^(th)` of its velocity while piercing a wooden plank. Then the number of such planks required to stop the bullet isA. 6B. 9C. 11D. 13

A bullet travelling horizontally looses `1//20^(th)` of its velocity w

1.	A bullet travelling horizontally looses `1//20^(th)` of its velocity while piercing a wooden plank. Then the number of such planks required to stop the bullet isA. 6B. 9C. 11D. 13
Answer» Final velocity after passing through a plank `v=(19u)/(20)` So, `v^(2)=u^(2)+2as,2as=-(39)/(400)u^(2)` if bullet passes through n plands and stoopped. `0=u^(2)+2as,u^(2)+2a(ns).` `n=-(u^(2))/(2as)=(400)/(39)=10.3` `"So,"(n=1)`

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A bullet travelling horizontally looses `1//20^(th)` of its velocity while piercing a wooden plank. Then the number of such planks required to stop the bullet isA. 6B. 9C. 11D. 13

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