A particle moving in a straight line covers half the distance with speed of `3 m//s`. The half of the distance is covered in two equal intervals with speed of `4.5 m//s and 7.5 m//s` respectively. The average speed of the particle during this motion is :

Explanation

`t_(1) =(s//2)/3 =(S)/(6), t_(2)=s_(1)/(4.5) =s_(2)/(7.5)`
.
`S_(1)+S_(2)=s//2`
`rArr 4.5 t_(2)+7.5 t_(2) =S//2`
`rArr t_(2)=(S)/(24)`
Average speed `=(S)/(t_(1)+2t_(2)) =4 ms^(-1)`.