A particle moving along a straight line covers half of the distance with a speed of `3ms^(-1)`. The other half of the distance is covered in two equal time intervals with speed of `4.5ms^(-1)` and `7.5ms^(-1)`. The average speed of the particle (in `ms^(-1)`) is

Options

A. A)`5.0`
B. `B)5.5`
C. C)`5.8`
D. D)`4.0`

Answer

D

Explanation

Average speed of the particle for other half of the distances.
`A_(v)=(2xx4.5xx7.5)/(4.5+7.5)`
`=(67.5)/(12)=5.62`
Again, the average speed of the particle
`A_(v.)=(2xx5.63xx3)/(5.63+3)`
`=3.9m//s=4m//s`