Question 1144062
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A body {{{highlight(cross(which))}}} {{{highlight(cross(is))}}} uniformly {{{highlight(cross(retarded))}}}  <U>decelerates</U> to {{{highlight(the)}}} rest in 10 sec after travelling a distance of 20 m. 
Calculate the initial velocity.
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<U>Solution</U>


<pre>
Let "a" be the deceleration value (now unknown) and let "t" be the duration of the decelerated move.


Then from Physics,  L = {{{(at^2)/2}}},  where L is the distance to get stop.


In your case,  L = 20 m, t = 10 seconds,  so


    a = {{{(2*L)/t^2}}} = {{{(2*20)/10^2}}} = {{{40/100}}} = 0.4 {{{m/s^2}}}.


Then for initial velocity v,  v = at = 0.4*10 = 4 {{{m/s}}}.    <U>ANSWER</U>
</pre>