Physics in Depth

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. D