Question

19. A body moving along straight line covers a distance
in three equal parts with speed 2 m/s, 3 m/s and
4 m/s, then its average speed is
​

Answer 1

Answer:

Average speed of the body will 2.7 m/s

Step by step explanations :

given that,

A body moving along straight line

covers a distance in three equal parts

with speed

2 m/s, 3 m/s and 4 m/s,

let the total distance covered by the body be d

so,

distance covered at 2 m/s = d/3

so,

time taken = distance covered/speed

time taken = (d/3)/2

= d/6 s

distance covered at 3 m/s = d/3

time taken = (d/3)/3

= d/9 s

distance covered at 4 m/s = d/3

time taken = (d/3)/4

= d/12 s

now,

Average speed =

total distance covered/total time taken

total time taken = d/6 + d/9 + d/12

= (6d + 4d + 3d)/36

= 13d/36

now,

we have,

total distance covered = d

total time taken = 13d/36

so,

Average speed = d/(13d/36)

= 36d/13d

= 36/13

= 2.76

so,

Average speed of the body will

2.7 m/s

Answer 2

Average speed of the body= 2.7 m/s

Step by step explanations :

given,

let total distance covered = 3d

speed for d = 2 m/s

time = d/2

speed for d = 3 m/s

time = d/3

speed for d = 4 m/s

time = d/4

Average speed =

total distance covered/total time taken

= 3d/(d/2 + d/3 + d/4)

= 12 × 3d/(6d + 4d + 3d)

= 36d/13d

= 36/13

= 2.76

so,

Average speed of the body will 2.7 m/s