A single polarizer will stop 50% of the incoming light.
When an object turns around an internal axis (like the Earth turns around its axis) it is called a rotation. When an object circles an external axis (like the Earth circles the sun) it is called a revolution.
The spiral structure of the milky way can be explained by long lived quasi-static density waves<em>, </em><em>according to the lin-shu hypothesis. </em>Curiously, the waves of higher density gas and stars (seen as spiral arms) appear to remain static as stars move around the galaxy. This explained by assuming that the gravitational disturbances cause by the 'clumping' material in the arms does not affect the gravitational field of the galaxy as whole and is therefore negligible.
source: Astrophysicist
Answer:
a) La aceleración angular es: 
b) El engranaje gira 125 radianes.
c) El engranaje hara aproximadamente 20 revoluciones.
Explanation:
a)
La aceleración angular se define como:

Donde:
- Δω es la diferencia de velocidad angular (en otras palabras ω(final)-ω(inicial))
- Δt es el tiempo en el que occure el cambio de velocidad angular


b)
El desplazamiento angular puede ser calculado usando la siguiente ecuación:

Aqui el angulo inicial es 0, por lo tanto.


El engranaje gira 125 radianes.
c)
Lo que debemos hacer aquí es convertir radianes a revoluciones.
Recordemos que 2π rad = 1 rev
Entonces:

Por lo tanto el engranaje hara aproximadamente 20 revoluciones.
Espero te haya sido de ayuda!
I only know about the Water tank which is the most accurate. You place your body in it, and weights are added I think. Somehow some measurements are gathered to get your body fat weight. Online calculators exist, as well as electronic waves that are sent int your body, the echo is recorded and analyzed.