Physics in Depth

Pullinger's Apparatus: Coefficient of Linear Expansion Pullinger's Apparatus Figure: Pullinger's Apparatus Pullinger's apparatus is a laboratory instrument used to determine the coefficient of linear expansion of a metal rod. Description A long cylindrical metal steam jacket (or hollow tube) encloses the experimental metal rod AB . The thermometer T is inserted into the side of the jacket to measure the temperature of the system (steam/rod environment). A spherometer is placed at the top on a stable base plate to precisely measure the tiny change in the rod's length. A galvanometer ( G ) is connected to a battery through the key ( K ) to signal the accurate reading position when an electrical contact is established. Working Principle The initial length of the rod \((L_1)\) is measured at room temperature \((\theta_1)\). With the lowering of the central leg of the sphe...

NEB Grade XII 2079 (2022) Physics Question Solution New Course Group 'A' Rewrite the correct options of each question in your answer sheet. If L represents momentum, I represents moment of inertia, then \(\frac{L^2}{2I}\) represents Rotational kinetic energy Torque Power Potential energy Solution: Option (a) Explanation: Since, the rotational kinetic energy is commonly expressed as, \[\text{K.E.}=\frac{1}{2}mv^2\] Also, \[L=I\omega\] Then, \[\begin{align*} \text{K.E.}&=\frac{1}{2} I \times \frac{L^2}{I^2}\\ &=\frac{L^2}{2I}\\ \end{align*}\] Starting from mean position, a particle in simple harmonic motion takes time \(T_1\) and \(T_2\) to cover first half and next half displacement in moving from mean to extreme position, then ...

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Model Question Solution Group 'A' Which of the following is a correct formula for calculating radius of gyration of a rotating object? Solution: Option (a) k\(^2=\frac{I}{m}\) Explanation \[I=MK^2\] \[\therefore K^2=\frac{I}{M}\] A horizontal stream of air is blown under one of the pan balance as shown in the figure. What will be the effect on the pan? Solution: Option (b) goes down Explanation Bernoulli's theorem for the stream line flow of an ideal liquid (incompressible and non viscous) gives, \[\begin{align} \frac{P}{\rho} + gh + \frac{v^2}{2}&=\text{constant}\\ \frac{P}{\rho} + \frac{v^2}{2}& =\text{constant} \hspace{0.1cm} \because \text{two pans are at same height}\\ \end{align}\] When v goes up, P goes down. For the above expression to be constant. So, pressure above the pan is high and that below is low. Du...