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

First we will convert the time into seconds

Total time = 2 minutes 20 seconds

= 2× 60 seconds + 20 seconds

= 120 seconds + 20 seconds

= 140 seconds

 According to Question

 If in 40 seconds farmer makes⇒ 1 Round
 
Then in 140 Seconds, The Farmer makes⇒ 1/40 x 140 Rounds
                                                   = 3.5 Rounds

If the farmer starts from position A (see figure), then after three complete rounds, he will reach at starting position A.



But in the next half round, the farmer will move from A to B, and B to C, so that his final position will be at C.

Hence, the total displacement(Shortest Distance) of the farmer will be AC.

Now,We know ABC is a right angled triangle as all the sides are of equal length with 90^o angle between them

So, Using Pythagoras Theorem,  (hypotenuse)²=(base)²+(perpendicular)³

(AC)² = (AB)² + (BC)²

(AC)² = (10)² + (10)²  (Given in the Question)

(AC)² = 100 + 100

(AC)² = 200

AC = 14.143 m

Hence, the magnitude of displacement( Distance from A To C) of the farmer at the end of 2 minutes and 20 seconds will be 14.143 meters.