The motion of a body is depicted graphically as shown in the given figure. Then the average speed of the body is ______ `m ^(-1)`

Options

A. 2
B. zero
C. 200
D. 20

Answer

A

Explanation

Let the distance between A and B be x m.
The velocity during its first half of the journey = 72 km `h^(-1)`
` 72 xx 5//18 m s^(-1)`
` 20 ms ^(-1)` ,
ltbr. The velocity during is second half of the journey= 36 km `h^(-1)`
` 36 xx 5//18 m s^(-1)`
`10 m s^(-1)`
The time taken to travel the first half of the distance
`t_(1) = (x//2)/20 = x/40 s `
Similarly, the time taken to travel the second half of the distance = `(t_(2))= (x//2)/10 = x/20 s`
The total time taken ` (T) = t_(1) +t_(2)`
`(x/40 +x/20) s`
`= ((x+2x)/40) s= (3x) /40 s`
Average veiocity = `(" total displacment")/("total time taken")`
`(x/(3x//40)) m s^(-1) = 40/3 m s^(-1)`
` 13.33 m s^(-1)`
` 13. overline3 ms ^(-1)`