Question 620: Centre of Mass and Rotational Motion

Question

The moment of inertia of a thin rod about an axis passing through its mid point and perpendicular to the rod is $$2400 \mathrm{~g} \mathrm{~cm}^2$$. The length of the $$400 \mathrm{~g}$$ rod is nearly:

Accepted Answer

$$
\begin{aligned}
& 	ext { Moment of inertia of rod }=I=\frac{m \ell^2}{12} \
& \Rightarrow \quad 2400=400 \frac{\ell^2}{12} \
& \Rightarrow \quad 72=\ell^2 \
& \Rightarrow \quad \ell=\sqrt{72}=8.48 \mathrm{~cm} \simeq 8.5 \mathrm{~cm}
\end{aligned}$$

Answer

8.5 cm

Answer

17.5 cm

Answer

20.7 cm

Answer

72.0 cm

Centre of Mass and Rotational Motion

The moment of inertia of a thin rod about an axis passing through its mid point and perpendicular to the rod is $2400 \mathrm{~g} \mathrm{~cm}^2. The length of the 400 \mathrm{~g}$ rod is nearly:

Choose the correct answer: