Ncert Class 9th Physics Chapter1 Motion Exercise1

Que1: An object move through distance can it have zero displacement?

If yes support your answer through an example.

Ans1: Yes it can have zero displacement because displacement is measure of of length from mean position to present position while distance us measure of the total length an object travels

For example there are two points A and B two meter apart now if a boy is in point and he first goes A to B then comes back to A then displacement will be zero because he is in his mean position but distance will be 4m because he first covered 2m while going from A to B then from B to A

Que2: A farmer moves along the boundary of square field of side 10m in 40sec what will be the magnitude of displacement at the end of 2min 20sec.

Ans: The farmer moves along the boundary of field in 40sec

So the distance covered by him will be = 4*10= 40m

The distance covered by him in 2min 20 sec will be = 40/40*140

= 140m

Now 140/40= 3.5 rounds of field so there will be two cases

If he start from center of side his 3.5 round will end on the middle of side just parallel to the side he was previously before starting so the displacement will be 10m

If he starts from the corner of the field his 3.5 round will end in diagonally opposite corner so his displacement will be = (10²+10²)½

= 14.14 m

Que3: which of the following is true for displacement

a) it cannot be zero

b) its magnitude is greater than distance travelled by an object.

Ans3:

a) not true because displacement can be zero if starting position and ending position is same.

b) not true

Because displacement is shortest measurable length between the mean position to end position but distance is measure of total length travelled by an object.