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} $
