Question

11. From the top of a tower of height 78.4 m two stones are projected
horizontally with 20 m/s and 30 m/s in opposite direction on reaching
the ground, their separation is
1) 100 m
2) 200 m
3) 50 m
4) 400 m​

Answer 1

The separation between the stones is 200 m.

Explanation:

Given data:

• Height of tower "h" =78.4 m
• Speed of stone 1 = 20 m/s
• Speed of stone 2 = 30 m/s

x1 = uxt1

x1 = 20 m/s

t1 = √ 2.h / g

x1 = 20 m/s x √ 2.h / g  = 20 √ 2.h / g --- (1)

x2 = ux2t2

x2 = 30 x c = 30 √ 2.h / g  ---- (2)

x1 + x2 = 20 √ 2.h / g + 30 √ 2.h / g

Separation (x1 + x2 ) = 50 √ 2.h / g

Separation (x1 + x2 )  = 50 x √ 2 x 78.4 / 10

Separation (x1 + x2 )  = 50 x √  156.8 / 9.8

Separation (x1 + x2 )  = 50 x  √ 16

Separation (x1 + x2 )  =  50 x 4 = 200 m

Thus the separation between the stones is 200 m.

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