A particle starts from rest and traverses a distance l with uniform acceleration, then moves uniformly over a further distance 2l and finally comes to rest after moving a further distance 3l under uniform retardation. Assuming entire motion to be rectilinear motion the ratio of average speed over the journey to the maximum speed on its ways is

Options

A. ` 1//5`
B. ` 2//5`
C. ` 3//5`
D. ` 4//5 `

Answer

C

Explanation

Let v: maximum speed
`rArr " "l(1)/(2) vt_1 ,2l =v(t_2-t_1)3l, =(1)/(2) v ( t_3-t_2) `
`rArr t_1=2l//v,t_2=(4l)/(v) ,t_3=10l //v`
`rArr ` av . Velocity `=(l+2l+3l)/(10l//v) =(3v)/(5) rArr ("av.velocity ")/("m.ax.velocity ") =(3)/(5)`
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