Kinematics Question 388

Question: A ship A is moving Westwards with a speed of $ 10km{{h}^{-1}} $ and a ship B 100 km South of A, is moving Northwards with a speed of $ 10km{{h}^{-1}} $ . The time after which the distance between them becomes shortest, it’s

Options:

A) 5h

B) $ 5\sqrt{2}h $

C) $ 10\sqrt{2}h $

D) 0 h

Show Answer

Answer:

Correct Answer: A

Solution:

$ V _{A}=10( -\widehat{i} ) $

$ V _{B}=10( -\widehat{j} ) $

$ V _{BA}=10\widehat{j}+10\widehat{i} $

$ =10\sqrt{2}\text{ km/h} $

$ \text{distance OB=100 cos45}{}^\circ $

$ \text{=50}\sqrt{2}\text{ km} $



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