Load $L$ is attached to the movable pulley. A rope is fixed at a point in ceiling that passes through the movable pulley.
In order to lift the load $L$ by $X$ meters, the effort $E$ needs to travel the distance of 2X meters. (The entire rope needs to be pulled by $E$ for a distance of 2X.)
Now, Velocity Ratio equals (Distance traveled by $E$) divided by (Distance traveled by $L$)
So it becomes : $2X/X$. This equals to 2
Since it is a ratio. it has no units of measurement.

Both crane and flagpole comprises of pulley but not well. 

1. A simple machine is a mechanical device that changes the direction or magnitude of a force. In general, they can be defined as the simplest mechanisms that use mechanical advantage (also called leverage) to multiply force. Levers,inclined planes and pulleys are called simple machines

A single fixed pulley is a machine that only changes the direction of the force applied, not the amount.
The wheel of a fixed pulley does not move because the wheel is attached to some support.

A sing;e fixed pulley like the one having an ideal mechanical advantage of 1 since the effort force is equal to the load force.

$\displaystyle VR=\frac { Distance\quad moved\quad by\quad effort }{ Distance\quad moved\quad by\quad load } $
$\displaystyle MA=\frac { 2Effort }{ Effort } =2$
When effort mved a distance x load moved a distance = x/2
So, 
$\displaystyle VR=\frac { X }{ X12 } =\frac { 2X }{ X } =2$

Using a single movable pulley, the load can be lifted by applying an effort equal to half the load i.e. single movable pulley acts as a force multiplier.

Single fixed pulley is fixed to a rigid support whereas a single movable pulley is not fixed to a rigid support.

Weight of pulley does not affect mechanical advantage of single fixed pulley.

In single movable pulley, ideal mechanical advantage is 2. Its velocity ratio is 2. It is used as a force multiplier. Load moves in the direction of effort.

A movable pulley is a pulley allowed to have translational motion.

The mechanical advantage of a wheel and axle $= \displaystyle \frac{Radius  of  wheel}{Radius  of  the  axle} $      ..........  (1)
But $MA = \displaystyle \frac{load}{effort}$      .............    (2)
From (1) and (2)
$\displaystyle \frac{Radius  of  wheel}{Radius  of  the  axle} = \frac{load}{effort}$
$\displaystyle \frac{50  cm}{10  cm} = \frac{1000 \times  10  N}{effort}$
$Effort = \displaystyle \frac{1000  \times  10  \times 10}{50}$
$ Effort = 2000 N$

Yes it effects the effort required to lift the load as a crow bar of 7 m length provides greater effort arm than a crow bar of 5 m length. Thus crow bar of 7 m length requires lesser effort.

A single fixed pulley has an ideal mechanical advantage of 1 since the effort force is equal to the load force.
No, it cannot be used as a force multiplier, instead, it is used to change the direction of force applied.

$P=F.V=(1000+1000)0.5$
$=\dfrac{11000}{2}=5500=5.5kw$

Centrifugation is the process of separating suspended particles from a liquid by rotating the liquid at a high speed. The mixture is taken in a closed bottle and rotated at a high speed. The heavy particles settle at the bottom while light particles remain behind. This method is used to separate cream from milk

We know that for a single fixed pulley, Distance moved by effort is equal to the distance moved by load.
$ Distance\; moved \;by\; effort = x$
$\therefore Distance \;moved \;by \;load = x$

$Velocity\ Ratio = 3$

$Mechanical advantage = Velocity Ratio \times Efficiency $
$M.A = 3 \times \dfrac{60}{100} = 1.8$
$M.A = \dfrac{load}{effort} $
$\therefore load = M.A \times effort$
$\Rightarrow 1.8 \times 200 = 360kgf$