Answer :

According to Figure the height of tower is 100m, Assuming the two stones meet at point P which is at a height x from the ground, from this we get that distance between Point P and the top of tower is (100-x)

(i)Firstly, for the stone falling from top of tower:

Height, h = (100 - x)

Initial velocity, u = 0Time, t =?

*g*= 10 m/s

^{2 }(As the stone is falling down)

We know that,

Putting the values in above equation

(100 – *x)* = 0 × *t* +1/2× 10 × *t*^{2}

*x)*= 5

*t*

^{2}(i)

(ii)Now, for stone projected vertically upwards:

Height,*h*=

*x*

Initial velocity, u = 25 m/s

Time,*t*=?

*g* = -10 m/s^{2} (As the stone is going up)

We know that,

Putting the values in above equation

x= 25×t+1/2×(-10)×t

^{2}

*x* = 25*t* – 5*t*^{2} (ii)

Now, by adding (i) and (ii), we get:

100 – x + x = 5*t*^{2} + 25 *t* – 5*t*^{2}

*t*

*t* =

*t*= 4 s

**Therefore, the 2 stones will meet after a time of 4 seconds.**

100 – x = 5× (4)^{2}

100 – x = 80

*x*

*x* = 20m

**Therefore, the two stones will meet at a height of 20 m above the ground after 4 seconds**

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