A bullet, fired into a door gets embedded exactly at it's centre, causing the door to rotate about it's vertical axis, practically without friction, with an angular velocity of $0.625 \mathrm{rads}^{-1}$. The door is 1.0 m wide and weighs 12 kg . If the mass of the bullet is 10 g , find the speed with which it was fired. (Hint: The moment of inertia of the door about the vertical axis at one end is $\frac{M L^2}{3}$.
$645 \mathrm{~ms}^{-1}$
$342 \mathrm{~ms}^{-1}$
$124 \mathrm{~ms}^{-1}$
$500 \mathrm{~ms}^{-1}$
In the equation $X=G^{-1 / 2} h^{1 / 2} c^{5 / 2}$, where G- universal gravitation constant, $h$ - Planck's constant and c - velocity of light, the dimensions of X are that of
Stress
Energy
Upthrust
Momentum
Force constant of interatomic bond, in a certain element, is $7.1 \mathrm{Nm}^{-1}$. If the atom oscillates in SHM in a certain direction, what is its frequency?
Given: Mole weight of the given element is 108 g and Avagadro's number $=6.023 \times 10^{23} \mathrm{~g} \mathrm{~mol}^{-1}$
$3.45 \times 10^{22} s^{-1}$
$0.005 \times 10^{12} s^{-1}$
$1 \times 10^{12} s^{-1}$
$6.667 \times 10^{12} s^{-1}$
A circular coil of radius $r=10 c m$ having 300 turns carries a current of 2 A . The coil is suspended vertically in a uniform magnetic field of strength 0.7 T . If the plane of the coil makes an angle $30^{\circ}$ with the magnetic field, the torque needed to prevent it from turning is:
11.42 Nm
1.1 Nm
22.84 Nm
5.71 Nm
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