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Q: physics of movement ( Answered 4 out of 5 stars,   1 Comment )
Subject: physics of movement
Category: Science > Physics
Asked by: dudester123-ga
List Price: $15.00
Posted: 17 Aug 2006 13:25 PDT
Expires: 16 Sep 2006 13:25 PDT
Question ID: 757079
The earth spins on it's axis at approximately 2 mi/sec(795 mi/hr), it
spins around the sun at approximately 18.5 mi/sec(67,000 mi/hr), and
the sun along with all of the planets spins around the center of the
galaxy at 144 mi/sec(1/10th the speed of light. So how come we don't
feel all of that motion?
Subject: Re: physics of movement
Answered By: keystroke-ga on 17 Aug 2006 13:53 PDT
Rated:4 out of 5 stars
Earth moves very fast. It spins (rotates) at a speed of about 1,000
miles per hour and orbits around the sun at a speed of about 67,000
miles per hour.

We do not feel any of this motion because these speeds are constant.
The spinning and orbital speeds of Earth stay the same so we do not
feel any acceleration or deceleration. You can only feel motion if
your speed changes. For example, if you are in a car which is moving
at a constant speed on a smooth surface, you will not feel much
motion. However, when the car accelerates or when the brakes are
applied, you do feel motion.

This website also gives you a much deeper answer

" Why don't we feel earth's rotation?

In actuality, you do "feel" the Earth's rotation. You may not notice
it, but it does affect us in minor ways. The Earth is rotating from
east to west. This is why the sun rises in the east and sets in the
west. This rotation causes toilets to flush clockwise in the northern
hemisphere and counter-clockwise in the southern hemisphere. This
effect can also be observed in a similar fashion in people. [Moderator
Note: the effect from the rotation of the Earth diminishes quite
rapidly at smaller scales; in the end, the resultant Coriolis effect
on toilets, sinks, etc. is much too small to have a significant
contribution to the direction of water flow. Please see Prof. Suzanne
Willis' great answer for more. -- RJS].

If you walk from the north pole to the equator following a compass
bearing of due south, you will gradually begin to stray to the left
(or east). This is because as you move south, the Earth is moving west
under your feet to the west, so each step you take lands you slightly
further east than the last. It is also due to the fact that
successively lower (closer to the equator) lines of latitude span a
larger circular distance. Since the entire Earth must rotate at a
constant rotational velocity, a spot on the Earth at 10 degrees
latitude will have a higher absolute motion than a spot at 70 degree
latitude. So as you walk south your surroundings begin to move faster
and faster as you get left a little more behind with each step. By the
way, you move right (also to the east) in the southern hemisphere as
you walk north towards the equator for the same reason.

This all has to do with inertia and perspective. You have intertia of
rest and intertia of motion. We were born into a moving world so we
started off with intertia of motion. Since we are not accelerating or
decelerating (at least not fast enough for us to notice; the Earth's
rate of rotation has varied over time) we continue living in our
constantly spinning world. In the absense of this planet and
atmosphere and any other gravitational effects, we would remain
completely still in absolute space. What we notice on time scales we
can understand from day to day comes solely from our perspective of
our immediate surroundings. Since the Earth and atmosphere around us
do not seem to move in relation to our position, we have no sense of
motion. Even though the planet rotates about itself and about the sun,
and our solar system rotates within the galaxy, we only notice
movement of ourselves relative to our immediate surroundings. Take,
for example, flying in a plane. Once the plane has reached its
cruising speed, you no longer "feel" like you are traveling at over
500 mph. This is because the plane and the air mass within the plane
is not accelerating or decelerating. You do have a strong
gravitational pull from the Earth that makes it harder to walk forward
than backward in a plane. This doesn't apply, however, when physically
standing on the Earth.

So, at any given moment, you may be rotating thousands of km/hour due
to the Earth's rotation, rotating around the Sun at an even faster
rate, being swept through the galaxy in our limb of the Milky Way, and
being thrust through the universe as the galaxy moves. But we feel
quite stationary on our planet. Movement is all based on perspective
and since our perspective does not extend beyond our fixed
surroundings, we feel next to no movement or rotation. Just don't plan
a hike from the Northern Rockies to Baja California and expect to get
there by following your compass south. Even though we may not feel
like our rotating Earth has any effect on us, on very small distance
scales and very long time scales, it does."

dudester123-ga rated this answer:4 out of 5 stars
thanks for the answer............

Subject: Re: physics of movement
From: markvmd-ga on 17 Aug 2006 19:36 PDT
Is this why I keep falling off the treadmill and into the Starbux
that's just a little south of the gym?

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