Question

A stone is projected upwards with speed 10m/s from the top of a 200m high building and at the same time another stone is projected vertically upwards from the ground with the speed of 50m/s in the same line . The time after which they collide is A) 4s. B)5s. C)8s. D)6s

Answer 1

Answer:

ANSWER

Let the two stones meet at a distance of x mfrom the top of the tower, and 't' be the time taken. Let us assume the downward direction as positive.

For the stone that is dropped its initial velocity u=0ms−1 ; displacement s = x and acceleration = acceleration due to gravity (g).

Using s=ut+21at2,wegetx=(0)t+21gt2→(1).

For the stone that is projected vertically upwards, its initial velocity, u=−50ms−1; displacement s =-(200-x) and acceleration a =g.

using s=ut+21at2,weget−(200−x)=−50×t+1/2gt2200=50t−1/2gt2+x→(1)(2)Fromtheequations(1)and(2)wehave200=50t−1/2gt2+1/2gt2⇒200=50∴t=4s

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