Shots are fired simultaneously from the top and bottom of a vertical cliff with the elevation `alpha = 30^@`, beta `= 60^@`, respectively. The shots strike an object simultaneously at the same point. If `a = 10 (sqrt3)` m is the horizontal distance of the object from the cliff, then the height h of the cliff is A. 30 mB. 45 mC. 60 mD. 90 m

Shots are fired simultaneously from the top and bottom of a vertical c

1.	Shots are fired simultaneously from the top and bottom of a vertical cliff with the elevation `alpha = 30^@`, beta `= 60^@`, respectively. The shots strike an object simultaneously at the same point. If `a = 10 (sqrt3)` m is the horizontal distance of the object from the cliff, then the height h of the cliff is A. 30 mB. 45 mC. 60 mD. 90 m
Answer» Correct Answer - C c. `u_1cos alpha = u_2cosbeta` `30sqrt(3) = (u_(2)^(2)sin2beta)/g rArr 30sqrt(3) = (u_(2)^(2)sqrt(3))/(2g)` `rArr u_(2)^(2) = 600 or u_2 = 10sqrt(6)` `t_2 = (2u_2sin60^@)/g = (2(10sqrt(6))sqrt(3)//2)/10 rArr t_2 = sqrt(18)` `u_1 = (10sqrt(6)cos60^@)/(cos30^@) = 10sqrt2` `-h = 10sqrt(2)sin 30^@sqrt(18) - 1/2 10 (sqrt18)^2` `=30-90 rArr h = 60m` .

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