Question

From top of tower of height 80m ,2 stones are projected horizontally with 20m/s and 30m/sec in opposite directions. Find the distance between both the stones

Answer 1

you didnt mention at what time you want the distance. so i made an assumption that they have touched the ground

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Answer 2

"The distance between the two stones is 200 m.

Solution:

It is given that the time taken by both the stones to fall through height of 80 m is, calculated from the equation, $h=(\frac { 1 }{ 2 } )gt^{ 2 }$

${ t }={ \left( \frac {2h }{ g } \right) }^{ \frac { 1 }{ 2 } }={ \left( \frac { 2\times 80 }{ 10 } \right)}^{ \frac {1}{2} }=\quad 4{ s }$

We know that $g\quad =\quad 10\frac { m }{ { s }^{ 2 } }$ (for calculation purpose g is taken as 10 instead of $9.8\frac { m }{ { s }^{ 2 } }$

The horizontal distances covered by stone 1 and stone 2  

${ s }_{ 1 }\quad =\quad 20{ \quad \times \quad }4\quad =\quad 80{ m }$

${ s }_{ 2 }\quad =\quad 30{ \quad \times \quad }4\quad =\quad 120{ m }$

$s\quad =\quad s_{ 1 }\quad +\quad s_{ 2 }\quad =\quad 80\quad +\quad$

$120\quad =\quad 200m$"