Question

A boy walks on a horizontal road and travels 2.5km with constant speed 5km/h then he returns to the same point and walked with constant speed of 7.5km/h what is the [a] average velocity of a man during the whole journey [b] average speed of a man during the following intervals of time [1] 0 to 30 min
[2] 0 to 50 min
[3]0 to 40 min

Answer 1

Given,

• Time taken by man to go from his home to market = t1

= distance / speed

= 2.5/5

=1/2 h

• Time taken by man to go from market to his home = t2

=distance/speed

=2.5/7.5

=1/3h

Total time taken :-

t1 + t2

$= \frac{1}{2} + \frac{1}{3}$

$= \frac{5}{6} hours$

= 50 min.

To Find:-

• Average velocity
• Average speed

Calculations:-

In time interval of 0 to 50min,

Total distance traveled = 2.5+ 2.5 = 5km.

Total displacement = Zero

Now,

Average velocity = displacement/time =0

Average speed = distance /time

$= \frac{5}{ \frac{5}{6} }$

=6km/h

In time interval of 0 to 40 min.

Average velocity= Displacement/time

$= \frac{3.75}{ \frac{2}{3} }$

$= \frac{45}{8}$

=5.625km/h

Average speed = distance/ time

$= \frac{5}{ \frac{5}{6} }$

=6km/h