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Two hollow cylinders of radii ' 1 m ' and ' 2 m ' respectively have common geometrical aixs as shown in the figure.

A fly starts with a constant speed ' v ' and hits the outer cylinder at ' X ' from inside. If both the cylinder starts rotating with an angular velocity of '1 rad/s'. The fly strikes another point ' Y ' where the distance between ' X ' and ' Y ' is 10 \mathrm{~cm}. Assuming the fly moves radially, find the speed of the fly.

Option: 1

10m/s


Option: 2

20 m/s


Option: 3

30 m/s


Option: 4

40 m/s


Answers (1)

best_answer

Let the fly crosses the inner cylinder at time, t=0 and reaches the outer at time, t=t. As the fly moves radially.

    \begin{aligned} (R-r)=t v \\ t=\frac{(R-r)}{v} \\ t=\frac{1}{v} \end{aligned}

If the cylinder is rotating with an angular velocity of ' \omega ', then angular displacement of the cylinder in the same time interval well be:-

    \theta=\omega t=(1)\left(\frac{1}{v}\right)

    \frac{l}{R}=\left ( \frac{1}{v} \right )\\

    \begin{aligned} & v=\frac{R}{l}=\frac{2}{10 \times 10^{-2}}=\frac{2}{0.1} \\ & v=20 \mathrm{~m} / \mathrm{s} \end{aligned}

    

Posted by

Rakesh

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