A farmer moves along the boundary of a square field of side 10m in 40s. What will be the magnitude of displacement of the farmer at the end of 2 minutes 20 seconds from his initial position?

Side of the square = 10 m

Perimeter of the square = 4�10 = 40 m

He completes 1 round in 40 s.

So, speed = 40/40 = 1 m/s

So, distance covered in 2 min 20 s or 140 s is = 140 � 1 = 140 m

Number of rounds of the square completed in moving through 140 m is = 140/40 = 3.5

In 3 rounds the displacement is zero. In 0.5 round the farmer reaches the diagonally opposite end of the square from his starting point.

Displacement = AC = (AB^{2} + BC^{2})^{1/2} = (100+100)^{1/2} = 10?2 m