A-stone-is-thrown-vertically-upwards-with-velocity-20m-s-at-the-same-time-and-20m-vertically-above-a-second-stone-is-allowed-to-fall-After-whst-time-and-at-what-height-do-they-collide-take-

Question Number 6164 by sanusihammed last updated on 16/Jun/16

A s t o n e i s t h r o w n v e r t i c a l l y u p w a r d s w i t h v e l o c i t y 20 m / s .

a t t h e s a m e t i m e, a n d 20 m v e r t i c a l l y a b o v e . a s e c o n d s t o n e i s

a l l o w e d t o f a l l . A f t e r w h s t t i m e a n d a t w h a t h e i g h t d o t h e y

c o l l i d e ? .

t a k e g = 10 m / s^{2}

Commented by prakash jain last updated on 17/Jun/16

Let us say stone which is falling travels

distance x . Then stone thrown upwards

will travel distance 20 - x .

20 - x = u \cdot t - \frac{1}{2} {g t}^{2} = 20 t - 5 t^{2} (1)

x = 0 \cdot t + \frac{1}{2} {g t}^{2} = 5 t^{2} (2)

s u b s t i t u t i n g v a l u e o f x f r o m 2 t o 1 .

20 - 5 t^{2} = 20 t - 5 t^{2}

t = 1 s

x = 5 m (f r o m t h e t o p)