Ship A is sailing towards north-east with velocity) v → = 30 i ^ + 50 j ^   km   h - 1 &#160…

Ship A is sailing towards north-east with velocity) v=30i^+50j^ km h-1  where i^ points east and j^, north. The ship B is at a distance of 80 km east and 150 km north of Ship A and is sailing towards the west at 10 km h-1. A will be at the minimum distance from B in:
  1. 4.2 h
  2.  3.2 h
  3.  2.6 h
  4. 2.2 h

Solution

vrel=v1-v2=40i+50j
rrel=r1-r2=-80i-150j
tmin=vrel·rrelvrel2=-3200-7500402+5022
tmin=107004100=10741=2.6h

Asked in: JEE Main 2019 (08 Apr Shift 1)

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