Chapter 7

NCERT
Class 9
Science
Solutions
2. 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?

Question:

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?

Answer:

Total distance traveled by farmer in 

40s = 4×10 =40m

Total time taken =2 min×20 sec =140 sec

Total number of rounds  =140/40 =3.5

If the farmer starts from A, then after 3.5 rounds, he reaches to point ′C′.

Therefore, displacement =AC.

Now, ABCD is a square, then △AB  is a right-angled △.

Using Pythagoras theorem,

AC2=AB2+BC2⇒AC=√102+102=√200=10√2

AC= 10×1.414=14.14m

Hence, displacement =14.14m

Buy Latest Books

Teacher's Corner