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Model Paper 8 — Physics STD 11 Science — Question

Rajasthan BoardEnglish MediumSTD 11 SciencePhysicsModel Paper 81 Mark
MCQ
The instantaneous angular position of a point on a rotating wheel is given by the equation $\theta(t)=2 t^3-6 t^2$. The torque on the wheel becomes zero at
  • A
    $t =0.25 s$
  • B
    $t =0.5 s$
  • C
    $t=2 s$
  • D
    $t=1 s$
✓

Answer

(d) $t=1 s$
$
\begin{aligned}
& \text { Explanation: } \theta(t)=2 t^3-6 t^2 \\
& \omega=\frac{d \theta}{d t}=6 t^2-12 t \\
& \alpha=\frac{d \omega}{d t}=12 t-12=0 \\
& \Rightarrow t=1 s
\end{aligned}
$

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