Newton’s Laws
https://en.wikipedia.org/wiki/Isaac_Newton
Ever wonder why things happen the way they do? Sir Isaac Newton
developed three major laws of motion that explain things that are so relevant
in our daily lives. These laws began the
development of astrophysics and the understanding that physical laws applied on
Earth can also be applied to the entire universe. Additionally, Newton delivered the final
goodbye to the geocentric (Earth-centered) model, and the heliocentric
(Sun-centered) model became the official model of the solar system. Most importantly, however, is Newton’s creation
of the Universal Law of Gravitation.
So what are these amazing laws and why are they so relevant?
Newton’s Laws of Motion
First Law:
When there is no other
force acting on an object, objects in motion stay in motion, in the same
direction and at the same speed, and objects at rest stay at rest.
In other words, if you were to remove all forces on Earth
and roll a bowling ball on an infinitely long alley, it would continue rolling
forever in a straight line in the direction it was rolled in. However, this is not what we actually see happen
because of other external forces like air resistance and friction, or other
objects, stop the ball. A bowling alley
is not long enough to witness the eventual decrease in speed (unless it is
rolled extremely slowly with low force), but you do witness the stopping of the
bowling ball after it hits the pins.
Perhaps a better example that everyone understands would be
something that happens each morning.
When your alarm goes off, you know it’s time to get out of bed, but do
you actually? Of course not! But don’t blame yourself, blame Newton’s
first law! When you hear your alarm, you are at rest, and your body will stay
that way until you exhibit a force on yourself to get up. Looking at it in a more positive way, all it
takes to start the process of getting up is to start the motion off your bed
because the rest of your body will follow until you are stopped by the floor.
Hopefully now the phrase ‘roll out of bed’ makes complete
sense!
Second Law:
Force = mass x
acceleration (F = ma)
This law explains the relationship between an object’s
acceleration given a specific mass and force acted upon it. For example, it is easier to throw something
small and light versus something large and heavy across the distance of a
room. The difference is the mass of the
two objects, but if you were to use the same amount of force to throw both
objects, the lighter object would accelerate more than the heavier object.
This law is the reason why your friends will happily pass
you a pencil, but will give you a dirty look if you ask them to hand you your
heavy textbook. The textbook is a much
heavier mass and therefore requires more effort from your friend (more force)
to make sure it gets to you.
Third Law:
Every force is paired
with another force with an equal and opposite reaction.
This law explains why, for example, we don’t go crashing
through the ground with each step you take because the downward force you exert
on the ground is met by an equal upward force.
However, we have to remember that even though forces are equal, they can
act on objects with different masses, which is why motion still exists.
This is also why a little kid that has very little mass only
bounces in the air so high when they jump on a trampoline compared to if they
were to jump at the same time as an adult.
Together, if they jump closely to each other, the kid and adult would
create a larger mass and net force, which would result in a greater
acceleration for the kid.
Newton and Astronomy
While these are a few examples that show how applicable Newton’s
Laws of Motion are to things in our daily lives, we can’t forget that they are
highly relevant to astronomical ideas as well.
Newton’s First Law explains why Earth, for example, is in a
constant state of motion and will continue it’s orbital motion until another
object hits it, or becomes near enough for another object’s gravitation force
to change it’s path.
Newton’s Second Law explains why larger
planets, like Jupiter, that have larger masses and exert greater gravitation
forces accelerate objects around them more.
For example, as a result of Jupiter’s large mass and strong
gravitational forces, it can change the orbital paths of objects around it,
which is exactly what happened to the Comet Shoemaker – Levy 9. As the comet was passing nearby, Jupiter’s
gravitational pull caused the comet to collide with it, which created an
observable impact on the planet.
Finally, Newton’s Third Law explains why it is possible for
objects like rockets to be launched into space because the downward force onto
the ground forces the rocket up.
Finally, the force that we live
with 24/7: gravity! As seen in the equation, gravity depends on the mass of the
two objects involved and the distance between them. The force of gravity is stronger as mass
increases and is weaker as distance increases. This is why Jupiter, which has a large mass,
has a stronger gravitational force compared to Earth.
http://formulas.tutorvista.com/physics/force-of-attraction-formula.html
Of course, gravity is also the
reason why when we let go of an object it drops
to the ground, or continuing the example from earlier, if you were to actually
‘roll out of bed,’ you would fall to the ground; but gravity can be applied to
the astronomical universe as well. It is
particularly important in understanding the paths of planetary orbits. Why do they orbit the way they do? The simple
answer is because of gravity. The
gravitational pull of the Sun keeps the planets in their bounded orbital paths,
and the amount of time it takes for planets to complete a full orbit is related
to the planet’s mass and distance from the Sun, in addition to it’s own
gravitational pull.
It is clear how influential Newton
was, and continues to be, in the study of our universe. From ‘basic’ laws of motion to gravity, we
now have a better understanding of the world we live in thanks to Newton.
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