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Class –IX Motion (Page No. 100)

Answers

1. Yes, if an object has moved through a distance it can have zero displacement

because displacement of an object is the actual change in its position when it moves

from one position to the other. So if an object travels from point A to B and then

returns back to point A again, the total displacement is zero.

2. Distance covered by farmer in 40seconds = 4 x (10)m = 40m

Speed of the farmer = distance/time = 40m/40s = 1 m/s.

Total time given in the question = 2min20seconds = 60+60+20 =140seconds

Since he completes 1round of the field in 40seconds so in he will complete 3rounds

in 120seconds (2mins) or 120m distance is covered in 2minutes. In another

20seconds will cover another 20m so total distance covered in 2min20sec = 120 +20

=140m.

Displacement = √102 +102 =√ 200 = 10√2 m (as per diagram) = 10 x 1.414 = 14.14 m.

3. Both (a) as well as (b) are false with respect to concept of displacement.