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5.work,energy,power and collision — Physics STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 SciencePhysics5.work,energy,power and collision1 Mark
MCQ
Under the action of a force, a $2 \,kg$ body moves such that its position $x$ as a function of time $t$ is given by $x=\frac{t^2}{3}$, where $x$ is in metres and $t$ in seconds. The workdone by the force in first two seconds is .......... $J$
  • A
    $1600$
  • B
    $160$
  • C
    $16$
  • ✓
    $\frac{16}{9}$
✓

Answer

Correct option: D.
$\frac{16}{9}$
d
Answer (4)

$x=\frac{t^2}{3}\Rightarrow v=\frac{2 t}{3}$

$W=\Delta K \cdot E .=\frac{1}{2}(2)\left[\left(\frac{4}{3}\right)^2-0\right]$

$=\frac{16}{9}\,J$

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