Page 85 - Understanding NCERT Science 09

Q uestions Time object A in m object B in m
Table 7.1
1. An object has moved through a
Distance
Distance
distance. Can it have zero
travelled by
travelled by
displacement? If yes, support
your answer with an example.
9:30 am
2. A farmer moves along the
9:45 am 10 12
20
19
boundary of a square field of side
10:00 am 30 23
10 m in 40 s. What will be the
magnitude of displacement of the 10:15 am 40 35
farmer at the end of 2 minutes 20 10:30 am 50 37
seconds from his initial position? 10:45 am 60 41
3. Which of the following is true for 11:00 am 70 44
displacement?
(a) It cannot be zero.
(b) Its magnitude is greater than 7.2 Measuring the Rate of Motion
the distance travelled by the
object.

7.1.2 UNIFORM MOTION AND NON-
UNIFORM MOTION

Consider an object moving along a straight
line. Let it travel 5 m in the first second,
5 m more in the next second, 5 m in the
third second and 5 m in the fourth second.
In this case, the object covers 5 m in each
second. As the object covers equal distances
(a)
in equal intervals of time, it is said to be in
uniform motion. The time interval in this
motion should be small. In our day-to-day
life, we come across motions where objects
cover unequal distances in equal intervals
of time, for example, when a car is moving
on a crowded street or a person is jogging
in a park. These are some instances of
non-uniform motion.

Activity ______________ 7.5

• The data regarding the motion of two
different objects A and B are given in
Table 7.1.
• Examine them carefully and state
whether the motion of the objects is
(b)
uniform or non-uniform.
Fig. 7.2

74 SCIENCE

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