Define relative velocity of an object w.r.t. another. Draw position-time graph of two objects moving along a straight line, when their relative velocity is (i) zero and (ii) non-zero.

Explanation

(a) `S = a + bt^(2)`
Instantaneous velocity, .
`v = (ds)/(dt) = 2bt`
`therefore ` Velocity at ` t = 0 , v = 0`
Velcoity at = 3 s, V = `2 xx 3 xx 3 = 18 ms^(-1)` .
(b) ` t = 3 rArr S = 8 + 3 xx (3)^(2) = 35`
at `t = 6s`
`S = 8 + 3(6)^(2) = 116 m`
Average velocity `= (116-35)/(6-3) = (81)/(3) = 27 ms^(-1)`