A particle at rest starts moving with constant angular acceleration $4 \mathrm{rad} / \mathrm{s}^2$ in…

A particle at rest starts moving with constant angular acceleration $4 \mathrm{rad} / \mathrm{s}^2$ in circular path. At what time the magnitudes of its tangential acceleration and centrifugal acceleration will be equal?
  1. $0.4 \mathrm{~s}$
  2. $0.5 \mathrm{~s}$
  3. $0.8 \mathrm{~s}$
  4. $1.0 \mathrm{~s}$

Solution

In rotational motion, $\begin{aligned} & \omega=\omega_0+\alpha \mathrm{t} \\ & \omega=\alpha \mathrm{t} \end{aligned}$ $\text { ( } \because \omega_0=0 \text {; particle at rest.) }$ $\therefore \quad$ Centrifugal acceleration $\mathrm{a}=\omega^2 \mathrm{r}$ $\therefore \quad \mathrm{a}=\alpha^2 \mathrm{t}^2 \mathrm{r}$ Tangential acceleration $\mathrm{a}_{\mathrm{t}}=\alpha \times \mathrm{r}$ Given: $\mathrm{a}=\mathrm{a}_{\mathrm{t}}$ $\Rightarrow \alpha^2 \mathrm{t}^2 \mathrm{r}=\alpha \mathrm{r}$ $\mathrm{t}^2=\frac{1}{\alpha}=\frac{1}{4}$ $\therefore \quad \mathrm{t}=\frac{1}{2}=0.5 \mathrm{~s}$

Asked in: MHT CET 2023 (09 May Shift 2)

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