Chapter 07 Motion Questions-01
Questions
1. An object has moved through a distance. Can it have zero displacement? If yes, support your answer with an example.
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Answer
Yes, an object can have zero displacement even when it has moved through a distance.This happens when final position of the object coincides with its initial position. For example, if a person moves around park and stands on place from where he started then here displacement will be zero.
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?
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Answer
Given, Side of the square field $=10 m$
Therefore, perimeter $=10 m \times 4=40 m$
Farmer moves along the boundary in 40 s.
Displacement after $2 m 20 s=2 \times 60 s+20 s=140 s=$ ?
Since in $40 s$ farmer moves $40 m$
Therefore, in 1s distance covered by farmer $=40 / 40 m=1 m$
Therefore, in 140s distance covered by farmer $=1 \times 140 m=140 mNow$, number of rotation to cover 140 along the boundary= Total Distance / Perimeter
$=140 m / 40 m=3.5$ round
Thus, after 3.5 round farmer will at point $C$ of the field.
Therefore. Displacement $A C=\sqrt{(10 m)^{2}+(10 m)^{2}}$
$=\sqrt{100 m^{2}+100 m^{2}}$
$=\sqrt{200 m^{2}}$
$=10 \sqrt{2} m$
$=10 \times 1.414=14.14 m$
Thus, after 2 min 20 seconds the displacement of farmer will be equal to $14.14 m$ north east from intial position.
3. Which of the following is true for displacement?
(a) It cannot be zero.
(b) Its magnitude is greater than the distance travelled by the object.
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Answer
None of the statement is true for displacement First statement is false because displacement can be zero. Second statement is also false because displacement is less than or equal to the distance travelled by the object.
