Explanation:
(a)
Critical angle is the angle at the angle of refraction is 90°. After the critical angle, no refraction takes place.
Using Snell's law as:
Where,
is the angle of incidence
is the angle of refraction = 90°
is the refractive index of the refraction medium
is the refractive index of the incidence medium
Thus,
The formula for the calculation of critical angle is:
Where,
is the critical angle
(b)
No it cannot occur. It only occur when the light ray bends away from the normal which means that when it travels from denser to rarer medium.
Answer:
Feathers are great thermal insulators.
Explanation:
Feathers are great thermal insulators. The loose structure of down feathers traps air.
As a result, energy cannot be transmitted easily through down feathers. This means birds are insulated from cold air outside, plus their body heat doesn't escape easily either.
Human beings discovered that down feathers are good for insulation long ago. For example, documents from the 1600s show that Russian merchants sold “bird down" to the Dutch hundreds of years ago.
Today, down is used in all sorts of products, including coats, bedding, and sleeping bags, to help better insulate the user from cold weather. Down can be collected from many different types of birds, but most of today's supply comes from domestic geese.
If you have a down coat or comforter, is it all down? In the United States, laws require that products labeled “100 percent down" contain only down feathers.
If your product is labeled “down," it can contain a mixture of both down feathers and synthetic fibers. Not all down feathers are created equal, though.
Down insulation is rated on a measure called “fill power." The higher the fill power, the more the down insulates.
The highest fill-power rating — 1200 — goes to eiderdown, which comes from the Common Eider duck. Eiderdown tends to be expensive.
<h2>
Answer: 277.777 m</h2>
Explanation:
The situation described here is parabolic movement. However, as we are told that the rock was<u> projected upward from the surface</u>, we will only use the equations related to the Y axis.
In this sense, the movement equations in the Y axis are:
(1)
(2)
Where:
is the rock's final position
is the rock's initial position
is the rock's initial velocity
is the final velocity
is the time the parabolic movement lasts
is the acceleration due to gravity at the surface of the moon
As we know
, equation (2) is rewritten as:
(3)
On the other hand, the maximum height is accomplished when
:
(4)
(5)
Finding
:
(6)
Substituting (6) in (3):
(7)
(8) Now we can calculate the maximum height of the rock
(9)
Finally:
Answer:
Fy=107.2 N
Explanation:
Conceptual analysis
For a right triangle :
sinβ = y/h formula (1)
cosβ = x/h formula (2)
x: side adjacent to the β angle
y: opposite side of the β angle
h: hypotenuse
Known data
h = T = 153.8 N : rope tension
β= 44.2°with the horizontal (x)
Problem development
We apply the formula (1) to calculate Ty : vertical component of the rope force.
sin44.2° = Ty/153.8 N
Ty = (153.8 N ) *(sen44.2°)= 107.2 N directed down
for equilibrium system
Fy= Ty=107.2 N
Fy=107.2 N upward component of the force acting on the stake
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