Question

a man who starts walking towards market 15 km away from his home with a speed of 15 km/hr. he found that market is closed and returned back home in an auto with a speed of 18 km/ hr .after 70 minutes what is the average speed and average velocity?​

Answer 1

Answer:

Given:

Distance travelled in each half = 15 km

Walking speed = 15 km/hr

Auto speed = 18 km/hr

Time taken = 70 mins

To find:

• Average speed
• Average velocity

Definitions:

Average speed if the ratio of total distance to the total time taken to travel that specified distance.

Average velocity is the ratio of total Displacement to the total time taken .

Calculation:

Since the person starts and ends at the same point (i.e. his home) , his displacement is zero. And hence his average velocity is also zero.

For average speed :

$avg. \: v = \dfrac{total \: distance}{total \: time}$

$= > avg. \: v = \dfrac{30}{ (\frac{15}{15} + \frac{15}{18}) }$

$= > avg. \: v = \dfrac{30}{ (1 + \frac{5}{6}) }$

$= > avg. \: v = \dfrac{30}{ ( \frac{11}{6}) }$

$= > avg. \: v = \dfrac{180}{11}$

$= > avg. \: v = 16.3 \: m {s}^{ - 1}$

So final answer :

$\boxed{ \red{ \huge{ \bold{avg. \: v = 16.3 \: m {s}^{ - 1} }}}}$

Answer 2

Answer:

Explanation:

Given :-

Distance traveled in each half = 15 km

Speed of man = 15 km/hr

Speed of auto = 18 km/hr

Time taken  = 70 min

To Find :-

Average speed

Formula to be used :-

Average speed = Total distance/Tatal time

Solution :-

Total Time taken = 15/15 + 15/18 = 11/6

Putting all the values, we get

Average speed = Total distance/Tatal time

Average speed = 30/11/6

Average speed = 180/11

Average speed = 16.3 m/s

Hence, the Average speed is 16.3 m/s.

And therefore the person starts and ends at the same point,

Hence, the average velocity is also zero.