A singer, during his performance, stands on the edge of a circular turntable, and begins to walk along its edge with a speed of $1.5 \mathrm{~ms}^{-1}$ relative to the ground. The turn table is mounted on a frictionless vertical axle. Its radius R =3m and its moment of inertia about the axle is $150 \mathrm{~kg} \mathrm{~m}^2$. It is initially at rest. If the mass of the singer is 75 kg , the time taken by the man to complete one revolution is:
12.57 s
8.56 s
6.28 s
20.5 s
A pith ball of mass ' $m$ ' gram and charge ' $Q$ ' is suspended using a mass less silk thread near a large charged conducting metal sheet of area ' $A$ ' and surface charged density ' $\sigma$ '. If the silk thread makes an angle $\Theta$ with the metal sheet, then:
$\tan \theta \propto \sigma$
$\tan \theta \propto A$
$\tan \theta \propto m g$
$\tan \theta \propto \frac{1}{\sigma}$
The material selected for making a permanent magnet should have:
High coercivity, low permeability and high retentivity
Low coercivity, low permeability and low retentivity
Low coercivity, low permeability and high retentivity
High coercivity, high permeability and high retentivity
Calculate the vapour pressure that can help the formation of a spherical droplet of water of radius $6.25 \times 10^{-5} \mathrm{~m}$ at $22^{\circ} \mathrm{C}$. Given: The surface tension of water at the given temperature is $7.28 \times 10^{-2} \mathrm{Nm}^{-1}$.
$1.01 \times 10^5 \mathrm{~Pa}$
$2.33 \times 10^3 \mathrm{~Pa}$
$8.81 \times 10^3 \mathrm{~Pa}$
$6.64 \times 10^4 \mathrm{~Pa}$
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