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2.Motion in Straight Line
easy
The distance travelled by an object in time $t$ is given by $s =(2 \cdot 5) t ^2$. The instantaneous speed of the object at $t =5\,s$ will be $....\,ms ^{-1}$
A
$12.5$
B
$62.5$
C
$5$
D
$25$
(JEE MAIN-2023)
Solution
Distance $(s)=(2.5) t^2$
Speed $( v )=\frac{ ds }{ dt }=\frac{ d }{ dt }\left\{(2.5) t ^2\right\}$
$v =5\,t$
At $t =5, v =5 \times 5=25\,m / s$
Standard 11
Physics