Question #dea10

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Answer 1 · 2016-12-26T15:27:52

Considering rectilinear motion of the body with initial velocity $u$ and uniform acceleration $a$

As the body travels $1.8m$ in first 3sec

$1.8=u*3+1/2*a*3^2$
$=>0.6=u+1.5a.....[1]$

As the body travels $4m$ in first 8sec

$1.8+2.2=4=u*8+1/2*a*8^2$

$=>0.5=u+4a.......[2]$

Subtracting [1] from[2]

$2.5a=0.5-0.6=-0.1$

$=>a=-0.04ms^-2$

Inserting $a=-0.04$ in [2]

$0.5=u-4*(0.04)$

$=>u=0.66ms^-1$

velocity at the end of 9 sec
using equation $v=u+at$

$v=0.66-0.04*9=0.66-0.36=0.3ms^-1$