Question 295: Centre of Mass and Rotational Motion

Question

A rigid massless rod of length 3l has two masses attached at each end as shown in the figure. The rod is pivoted at point P on the horizontal axis (see figure). When released from initial horizontal position, its
instantaneous angular acceleration will be -
![](https://imagex.cdn.examgoal.net/oh8fXQLUXsKer6mIA/oQ48Ulp4E2Q9FsGgMntN3dne4v8tF/Jh9fiRdnCLNipMBYwjHOya/image.png)

Accepted Answer

Applying torque equation about point P.
2M
0
(2l) $-$ 5 M
0
gl = I$\alpha $
I = 2M
0
(2l)
2
+ 5M
0
l
2
= 13 M
0
l
2
d
$ 	herefore $  $\alpha $ = $-$ ${{{M_0}gl} \over {13{M_0}{\ell ^2}}}$ $ \Rightarrow $ $\alpha $ = $-$ ${g \over {13\ell }}$
$ 	herefore $  $\alpha $ = ${g \over {13\ell }}$ anticlockwise
![](https://imagex.cdn.examgoal.net/amxkBuep7VhCyomGe/f7FNpuTAMds5X2LklJDHYxXD2bbwW/cJ3OqAhSkFDuwNCBMnzW7g/image.png)

Answer

${g \over {13l}}$

Answer

${g \over {2l}}$

Answer

${g \over {3l}}$

Answer

${7g \over {3l}}$

Centre of Mass and Rotational Motion

A rigid massless rod of length 3l has two masses attached at each end as shown in the figure. The rod is pivoted at point P on the horizontal axis (see figure). When released from initial horizontal position, its instantaneous angular acceleration will be -

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