In Exercises 2.9 and 2.10, we have
carefully distinguished between
average speed and magnitude of average
velocity. No such distinction is necessary when
we consider instantaneous speed and
magnitude of velocity. The instantaneous speed
is always equal to the magnitude of
instantaneous velocity. Why?
A man walks on a straight road from
his home to a market 2.5 km away with
a speed of 5 km h–1. Finding the
market closed, he instantly turns and
walks back home with a speed of 7.5
km h–1. What is the
(a) magnitude of average velocity, and
(b) average speed of the man over the
interval of time (i) 0 to 30 min, (ii)
0 to 50 min, (iii) 0 to 40 min ?
[Note: You will appreciate from this
exercise why it is better to define
average speed as total path length
divided by time, and not as
magnitude of average velocity. You
would not like to tell the tired man
on his return home that his
average speed was zero !]
Explain clearly, with examples, the distinction between :
(a) magnitude of displacement (sometimes called distance) over an interval of time,
and the total length of path covered by a particle over the same interval;
(b) magnitude of average velocity over an interval of time, and the average speed
over the same interval. [Average speed of a particle over an interval of time is
defined as the total path length divided by the time interval]. Show in both (a)
and (b) that the second quantity
is either greater than or equal to
the first. When is the equality sign
true ? [For simplicity, consider
one-dimensional motion only].
2. Identify the next shape:
( sequence of shapes: triangle, square, pentagon, ?)
A) Hexagon
B) Octagon
C) Circle
+91 94284 01196
© Copyright 2025. Doubtora. All Rights Reserved
