Joseph jogs from one end A to the other end B of a straight 300 m road in 2 minutes 30 seconds and then turns around and jogs 100 m back to point C in another 1 minute. What are Joseph’s average speeds and velocities in jogging?

(a) From A to B

(b) From A to C

Firstly, we have to draw a line segment to show the movement of Joseph during his jogging:

(a) Given,

Total distance from A to B = 300 m

Total time taken = 2 minutes 30 seconds

= 2 × 60 + 30

= 120 + 30

= 150 s

Average speed (from A to B) =

=

= 2.0 m/s (i)

The displacement and the time taken of Joseph is same ingoing from A to B i.e., 300m and 150 s respectively.

Therefore, Average velocity (from A to B) =

=

= 2.0 m/s (ii)

So, from (i) and (ii) it is clear that the average speed and average velocity of Joseph during his jogging is same.

(b) Given,

Total distance from A to C = 300 + 100

= 400 m

Total time = 2 minutes 20 seconds + 1 minutes

= 150 s + 60 s

= 210 s

Average Speed (from A to C) =

=

= 1.90 m/s (iii)

Now the average velocity of Joseph from A to C:

Displacement = 300 – 100

= 200 m

Total time taken is same as that of the time taken from A to C i.e., 210 s

Average velocity (from A to C) =

=

= 0.95 m/s (iv)

From (iii) and (iv) it is clear that the average speed of Joseph is different from his average his velocity.