Answer
From the question we can see that the in medium 1 speed of light is 200,000 Km/s where as in Medium 2 speed of light is 250,000 km/s.
We can conclude that medium 1 is denser than Medium 2.
In third medium Light speed halts so, the third medium is opaque.
We can say that
Medium 1 can be either water, glass.
Medium 2 will be gas
Medium 3 will be an opaque material.
The key principle is that crank length, just like frame size, should be proportional to the rider height and then modified to what fits the individual. There are 4 charts, two for the upright position and two for the aero position, depending upon how you race.
Answer:
58.27 N
Explanation:
the data we have is:
mass: 
coefficient of friction: 
and we also know the acceleration of gravity is 
We need to do an analysis of horizontal and vertical forces acting on the object:
-------
Vertically the forces acting on the object:
- Normal force
(acting up from the object)
- weight:
(acting down from)
so the sum of forces in the vertical axis "y" are:

from Newton's second Law we know that
, so:

and since the object is not accelerating in the vertical direction (the movement is only horizontal)
, and:

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now let's analyze the horizontal forces
- frictional force:
and since
--> 
- force to move the object:

and the two forces just mentioned must be opposite, thus the sum of forces in the "x" axis is:

and we are told that the crate moves at a steady speed, thus there is no acceleration: 
and we get:

substituting known values:

A.is an example of decomposition reaction.