Aristotle's geocentric theory failed to match the expected predictions because a few celestial objects appear to have retrograde motion.
Answer: Option B
<u>Explanation:</u>
Aristotle’s theory states that all the bodies in universe rotate around the earth, and earth is located at the centre. But, the most serious challenge it was given was that, the difference found in the paths of revolution of mercury and Venus. They are revolving around the sun, and not the earth, periodically.
This is the significant drawback, and major factor for the Copernicus and the other models to be achieved. The mercury and Venus, closest planets to earth, and the sun too, are not following the earth’s path. And hence, upon studying clearly, all celestial bodies do not follow a path round the earth, but around a fireball, that is sun.
High tides and low tides are caused because of moon's gravitational force
Answer:
The cyclist's average speed is 13.43 
Explanation:
Speed is a quantity that expresses the relationship between the space traveled by an object and the time used for it. That is, speed is the magnitude that expresses the variation in position of an object and as a function of time, which would be the same as saying that it is the distance traveled by an object in the unit of time.
Average speed relates the change in position to the time taken to effect that change:

In this case:
- total distance traveled= 32 km + 15 km= 47 km
- total time= 3 hours that the cyclist travels + 30 minutes of rest = 3 hours + 0.5 hours (being 60 minutes equal to 1 hour, then 30 minutes equals 0.5 hours) = 3.5 hours
Replacing:

and solving, you get:
speed= 13.43 
<u><em>The cyclist's average speed is 13.43 </em></u>
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Answer:
E = k Q₁ / r²
Explanation:
For this exercise that asks us for the electric field between the sphere and the spherical shell, we can use Gauss's law
Ф = ∫ E .dA =
/ ε₀
where Ф the electric flow, qint is the charge inside the surface
To solve these problems we must create a Gaussian surface that takes advantage of the symmetry of the problem, in this almost our surface is a sphere of radius r, that this is the sphere of and the shell, bone
R <r <R_a
for this surface the electric field lines are radial and the radius of the sphere are also, therefore the two are parallel, which reduces the scalar product to the algebraic product.
E A = q_{int} /ε₀
The charge inside the surface is Q₁, since the other charge Q₂ is outside the Gaussian surface, therefore it does not contribute to the electric field
q_{int} = Q₁
The surface area is
A = 4π r²
we substitute
E 4π r² = Q₁ /ε₀
E = 1 / 4πε₀ Q₁ / r²
k = 1/4πε₀
E = k Q₁ / r²
Answer:
The answer is D- Coal is set aside to burn as heating fuel
Explanation:
Allocation decisions set aside resources for a specific purpose.