TMH- GS - PHYSICS

1) The universal law of gravitation was propounded by .......
a.kepler
b.Galileo
c.Newton
d.Copernicus

ans.Newton




Newton's Law of Gravitation states that the attractive
gravitational force existing between two bodies is
directly proportional to the product of their masses and
inversely proportional to the square of the distance
between them
so, for a system fo two bodies of mass M and m
separated by a distance R we have
F = GMm / R 2
G is a universal constant a fixed number also known as
Newton's Gravitational Constant which has the same
vale (of 6.67 x 10 -11 Nm 2 /kg2) everywhere in the
universe. It is an important universal constant and is
used to quantify the magnitude of the gravitational
force exerted between two or more objects.


2) The gravitational force with which the Sun attracts the earth
a. is less than the force with which the the earth attracts the Sun.
b. is the same as the force with which earth attracts the Sun
c. is more than the force with which the earth attracts the Sun
d. is constant through out the year.

ans. b

The earth's orbit is a perpendicular motion to
the gravitational force of the sun. If the
earth slowed, it would fall towards the sun,
if it slowed enough, it would fall into the
sun. If it sped up, it would get more distant
from the sun. If it sped up enough, it would
have the escape velocity to escape the solar
system.
Actually, both of these things happen... well,
not the falling into the sun and the escaping
orbit, but the earth's orbit is elliptical.
Kepler's Second Law tells us something about
the speed of a planet and it's proximity to
the sun. It goes faster when it is closer, and
slower when it is farther. So, when the earth
is farther away from the sun, it is orbiting
more slowly, this slower movement results in
the earth moving slightly closer to the sun.
But as it gets closer, it gains momentum...
which, in turn, makes it start to inch away.
Perihelion (closest approach to the sun) for
earth usually occurs on or around January 2,
while aphelion (farthest distance from sun)
is approximately around July 4. So, you'll be
happy to know that, in the northern
hemisphere, winter goes by slightly faster,
because we are near perihelion and our
planet "sweeps equal area in equal time" as
per Kepler's Second Law. Exciting I know.
Funny how you used the word equilibrium,
that's essentially what an orbit-system
establishes, as long as the orbit is stable.