Question

I went to a shop with a constant speed of 30 m/s and came back with 20 m/s. What is my average speed of travel?​

Answer 1

Answer:

24 m/s

Explanation:

Let the distance between those end points be d.

When going:

= > speed = distance/time

= > 30 = d/time

= > time = d/30

When returning:

= > speed = distance/time

= > 20 = d/time

= > time = d/20

Average speed = (total distance)/( total time)

= > Average speed = $\frac{d+d}{\frac{d}{20}+\frac{d}{30}}$

= > Average speed = $\frac{d(1+1)}{d(\frac{1}{20}+\frac{1}{30})}$

= > Average speed = $\frac{2}{\frac{20+30}{20*30}}$

= > Average speed = (2*30*20)/(20+30)

= > Average speed = 24 m/s

Answer 2

Answer:

Let the distance from A to B be x ,time taken be t1 and t2 and speeds be v1 and v2.

So, t1=x/v1————-(i)

And, t2=x/v2 ———(ii)

Now, according to the definition of average speed= Total distance/ total time

So, Vavg= 2x/[(x/v1)+(x/v2)]

Simplifying this you can write :-

Vavg= 2x/[x(v1+v2)/v1v2]

So, Vavg=2v1v2/(v1+v2)

Putting the values for v1=20m/sandv2=30m/s in the equation we can write :-

Vavg=(2×30×20)/50=24m/s.

In case of average velocity it is 0 m/s because the displacement is 0 as the body returns to its original position.