A) 20 m
B) 10.2 m
C) 11.2 m
D) 15.5m
Correct Answer: A
Solution :
Suppose the two stones meet at a height h from the ground. The stone that is dropped from above will cover (100 - h) before meeting the stone that is thrown from ground. Let, time taken is t. So, \[100-h=(0)t+\frac{1}{2}(10){{t}^{2}}\] Or \[100-h=5{{t}^{2}}\] ?(i) Similarly, for stone thrown from ground, \[h=25t-\frac{1}{2}(10){{t}^{2}}\] Or \[h=25t=-5{{t}^{2}}\] ?(ii) Adding (i) and (ii), 100 = 25t Or t=4 s Using (ii), \[h=25\times 4-5{{(4)}^{2}}=100-80=20m\]
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