A thin uniform rod ($X$) of mass $M$ and length $L$ is pivoted at a height $\left(\frac{L}{3}\right)$ as shown in the figure. The rod is allowed to fall from a vertical position and lie horizontally on the table. The angular velocity of this rod when it hits the table top, is __________.
($g = \text{gravitational acceleration}$)
To find the angular velocity of the rod when it hits the table, we can use the principle of conservation of energy. Initially, the rod is in a vertical position with its center of mass at a height of \(\frac{L}{2}\) from the pivot point. When it falls to the horizontal position, the center of mass is at a height of \(\frac{L}{3}\) from the pivot.
Step-by-step Solution:
First, calculate the initial potential energy (PEi) of the rod:
\(PE_i = Mgh\), where \(h = \frac{L}{2}\).
So, \(PE_i = Mg\frac{L}{2}\).
At the horizontal position, calculate the final potential energy (PEf).
The center of mass is at height \(\frac{L}{3}\):
\(PE_f = Mg\frac{L}{3}\).
Using conservation of energy:
Initial Potential Energy = Final Potential Energy + Rotational Kinetic Energy (KErot)
\(Mg\frac{L}{2} = Mg\frac{L}{3} + \frac{1}{2}I\omega^2\)
The moment of inertia \((I)\) of the rod about the pivot is:
\(I = \frac{1}{3}ML^2\) (using the parallel axis theorem).
Substitute \(I\) in the energy conservation equation:
\(Mg\frac{L}{2} - Mg\frac{L}{3} = \frac{1}{2} \times \frac{1}{3}ML^2 \omega^2\)
Simplify and solve for \(\omega\):
\(\frac{MgL}{6} = \frac{1}{6}ML^2\omega^2\)
Cancel \(M\):
\(gL = L^2\omega^2\)
\(\omega^2 = \frac{3g}{L}\)
Therefore, the angular velocity is:
\(\omega = \sqrt{\frac{3g}{L}}\).
Thus, the correct answer is \(\sqrt{\frac{3g}{L}}\).
In the given figure the blocks $A$, $B$ and $C$ weigh 4 kg, 6 kg and 8 kg respectively. The co-efficient of sliding friction between any two surfaces is 0.5. The force $\vec{F}$ required to slide the block $C$ with constant speed is ______ N. (Use $g = 10 \text{ m/s}^2$)

In the given figure the blocks $A$, $B$ and $C$ weigh 4 kg, 6 kg and 8 kg respectively. The co-efficient of sliding friction between any two surfaces is 0.5. The force $\vec{F}$ required to slide the block $C$ with constant speed is ______ N. (Use $g = 10 \text{ m/s}^2$)
