A simple pendulum of length $l$ has a bob of mass $m$ ,with a charge $q$ .On it a vertical sheet of charge, with surface charge density'$\sigma$'passes through the point of suspension.At equilibrium,if the string makes an angle $\theta$ with the vertical,then
$\tan \theta=\frac{\sigma q}{2 \varepsilon_0 m g}$
$\tan \theta=\frac{\sigma q}{\varepsilon_0 m g}$
$\cot \theta=\frac{\sigma q}{2 \varepsilon_0 m g}$
$\cot \theta=\frac{\sigma q}{\varepsilon_0 m g}$
The equation of a transverse wave is $y=y_0 \sin 2 \pi\left(f t-\frac{x}{\lambda}\right)$ .If the maximum particle velocity be four times that of wave velocity then
$\lambda=\frac{\pi y_0}{4}$
$\lambda=\frac{\pi y_0}{2}$
$\lambda=\pi y_0$
$\lambda=2 \pi y_0$
A uniform but time varying magnetic field is present in a circular region of radius ' $R$ '. The magnetic field is perpendicular and into the plane of loop and the magnitude of field is increasing at a constant rate $\alpha$. There is a straight conducting rod of length 2 R placed as shown in figure. The magnitude of induced emf across the rod is

$\pi \mathrm{R}^2 \alpha$
$\frac{1}{2} \pi \mathrm{R}^2 \alpha$
$\frac{1}{\sqrt{2}} \mathrm{R}^2 \alpha$
$\frac{1}{4} \pi \mathrm{R}^2 \alpha$
From a tower of height $H$ ,a particle is thrown vertically upwards with a speed $u$ .The time taken by the particle to hit the ground is $n$ times that taken by it to reach the highest point of its path.The relation between $H, u$ and $n$ is
$2 g H=n^2 u^2$
$g H=(n-2)^2 u^2$
$2 g H=n u^2(n-2)$
$2 g H=u^2(n-2)^2$
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