Question

The distance between two points A and B is 100 m. A person moves from A to B with a speed of 20 m/s and from B to A with a speed of 25 m/s. Calculate average speed ?​

Answer 1

*Given :

• Distance between A and B = 100 m
• Speed from A to B = 20 m/s
• Speed from B to A = 25 m/s

*To find :

• Average speed
• Average speedAverage Velocity

*Solution :

Total distance covered in the journey = 2 × Distance between A and B

$= 2 \times 100$

$= 200 \: m$

We know that

$Time = \frac{distance \: travelled}{speed}$

*Time taken when the speed is 20 m/s from A to B

$→ t_{1} = \frac{100}{20}$

$= 5 \: sec$

Time taken when the speed is 25 m/s from B to A

$→ t_{2} = \frac{100}{25 } \\ \\ = 4 \: s$

Total time taken in the whole journey is given by

$t = t_{1} + t_{2}$

$t = 5+4 \: t \\ = 9 sec$

• The total time taken in the journey is 9 s.

Substituting values in the formula of average speed :

$→Average \: \: speed= \frac{Total \: distnce}{Total \: time}$

$= \frac{200}{9} {ms}^{ - 1}$

$∴average \: speed=22.23 {ms}^{ - 1} </p><p>$

Total displacement covered = 100 - 100

= 0 m (as the initial and final points are same)

• Average velocity is given by :

$Average \: velocity= \frac{Displacement }{Time}$

$average \: velocity = \frac{0}{9}$

$∴ \: average \: velocity \: = \: 0 \: {ms}^{ - 1}$

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Answer 2

Answer:

Speed while going from A-B= 20m/s

Time taken= distance/speed

                  = 100/20

                  = 5s

Speed while going from B-A= 25m/s

Time taken= distance/speed

                  = 100/25

                   = 4s

Total time taken in whole journey= 5s+4s = 9s

Total distance covered in whole journey= 100m+100m = 200m

Average speed= total distance/ total time

= 200/9

= 22.22 m/s

Explanation:

Hope it seems easy & helpful