The height at which the weight of a body becomes $1/16^{th}$ of its weight on the surface of the earth (radius $R$) is: (in $R$)

In an $NPN$ transistor,$10^{10}$ electrons enter the emitter region in $10^{-6} \, s$. If $2\%$ of electrons are lost in the base region,then the collector current and the current amplification factor $(\beta)$ are,respectively:

The inverse point of $(1,2)$ with respect to the circle $x^2+y^2-4x-6y+9=0$ is

The magnetic needle of a tangent galvanometer is deflected at an angle $30^{\circ}$ due to a magnet. The horizontal component of the Earth's magnetic field is $0.34 \times 10^{-4} \text{ T}$,which is along the plane of the coil. The magnetic field due to the magnet is:

$A$ block of mass $1\, kg$ lies on a horizontal surface in a truck. The coefficient of static friction between the block and the surface is $0.6$. If the acceleration of the truck is $5\, m\, s^{-2}$,the frictional force acting on the block is ........ $N$.

If $a = \hat{i} + \hat{j} + t \hat{k}$ and $b = \hat{i} + 2 \hat{j} + 3 \hat{k}$,then the values of $t$ for which $(a+b)$ and $(a-b)$ are perpendicular are: