What is the order of reactivity of halogen acids with $C_2H_5OH$?

$\frac{(1+i)^{2011}}{(1-i)^{2009}}$ is equal to

$A$ particle of mass $m$ and charge $q$ moves with a constant velocity $v$ along the positive $x$ direction. It enters a region containing a uniform magnetic field $B$ directed along the negative $z$ direction,extending from $x = a$ to $x = b$. The minimum value of $v$ required so that the particle can just enter the region $x > b$ is

$A$ pulley of radius $2\, m$ is rotated about its axis by a force $F = (20t - 5t^2)\, N$ (where $t$ is measured in seconds) applied tangentially. If the moment of inertia of the pulley about its axis of rotation is $10\, kg\, m^2$,the number of rotations made by the pulley before its direction of motion is reversed,is

Two blocks $A$ and $B$ of masses $1\,kg$ and $2\,kg$ are connected together by a spring and are resting on a horizontal surface. The blocks are pulled apart so as to stretch the spring and then released. The ratio of $K.E.s$ of both the blocks is

When a wave travels in a medium,the particle displacements are given by $y = a \sin 2\pi (bt - cx)$ where $a, b,$ and $c$ are constants. The maximum particle velocity will be twice the wave velocity if