Question

A stone is allowed to fall from the top of a tower 120m high and at the same time another stone is projected vertically upward from the ground with a velocity of 40m/s . Calculate when and where two stones will meet

Answer 1

let "t" = time after which both stones meet

"S" = distance travelled by the stone dropped from the top of tower

(100-S) = distance travelled by the projected stone.


◆ i) For stone dropped from the top of tower

-S = 0 + 1/2 (-10) t²

or, S = 5t²


◆ ii) For stone projected upward

(100 - S) = 25t + 1/2 (-10) t²

= 25t - 5t²


Adding i) and ii) , We get

100 = 25t

or t = 4 s


Therefore, Two stones will meet after 4 s.


◆ ¡¡¡) Put value of t = 4 s in Equation i) , we get

S = 5 × 16

= 80 m.


Thus , both the stone will meet at a distance of 80 m from the top of tower.

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