14)A moving boat is observed from the top of a 150 m high cliff moving

1.	14)A moving boat is observed from the top of a 150 m high cliff moving away from thediff. The angle of depression of the boat changes from 60째 to 45째 in 2 minutes. Find[CBSE 2017]psPs the speed of the boat in m/h.
Answer» Find the distance of boat from cliff when angle of elevation is 60° by taking tan60 = height of cliff /distance between boat and cliff it is found that it is 50√3 now in the same way taking angle of elevation as 45°find distance of boat when it is 45 °from the cliff. on finding distance = 150 m now find the distances between two position of boats which is 150 - 50√3 = 50(3 -1.732) = 63.4the boat travels 63.4 m in 2 min or 120 sec:. speed of boat = distance / time itis wanted m/hr:. answer should be multiplied by 3600=63.4×3600/120 =1902 m/hr

14)A moving boat is observed from the top of a 150 m high cliff moving away from thediff. The angle of depression of the boat changes from 60째 to 45째 in 2 minutes. Find[CBSE 2017]psPs the speed of the boat in m/h.

Answer»

Find the distance of boat from cliff when angle of elevation is 60° by taking tan60 = height of cliff /distance between boat and cliff it is found that it is 50√3

now in the same way taking angle of elevation as 45°find distance of boat when it is 45 °from the cliff. on finding distance = 150 m now find the distances between two position of boats which is 150 - 50√3

= 50(3 -1.732) = 63.4the boat travels 63.4 m in 2 min or 120 sec:. speed of boat = distance / time itis wanted m/hr:. answer should be multiplied by 3600=63.4×3600/120 =1902 m/hr

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