#### • Class 11 Physics Demo

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#### • how fast does the earth rotate near the equator

Question:a. The atmosphere of Venus is only about one tenth as thick as the earth's atmosphere. b. The atmosphere of Venus contains about 2.5 times more O2 then the earth's atmosphere. c. The atmosphere of Venus doesn't trap heat nearly as well as the atmosphere of the Earth. d. The atmosphere of Venus gets steadily colder with height while the Earth's varies with height.

Question:The Earth rotates anticlockwise as viewed from above the north pole. As it rotates the only thing causing the atmosphere to rotate with it is friction between air and the Earth's surface. So the air should rotate but at a slower speed than the solid part of the Earth, which means that an observer standing on the Earth should experience the air rushing past in the opposite direction to the Earth's rotation. This would be a very strong wind from east to west all over the Earth. Yet the air doesn't do that! Why not? Old Know All: The same forces? You're saying that there is a force which drives the Earth to rotate? So what IS the force which does this? I thought the rotation was something continuing since the Earth originally formed (not significantly slowing because there's almost no friction in the vacuum of space).

Answers:The rotating earth imparts a force, via friction, to the atmosphere. This causes the atmosphere to move with the earth. There is no friction between the atmposphere and the vacuum of outer space. So there's really only one force imparting a net movement to the atmosphere, so the force doesn't have to be that strong and there won't be any shear forces along the thickness of the atmosphere. Sure there's inertia, but there's millions of years for the atmosphere to accelerate until it matches the speed of rotation of the earth. Since F=MA the atmosphere will acelerate until F=0 when the earth and the atmosphere will be moving at the same speed. Astronomers actually found a planet (moon) in the solar system where they predicted that there would be very little wind because there was very little heating of the atmosphere. Turns out that the wind was something like 2,000 miles per hour because the lack of heat meant that there was very little turbulence to slow down the net movement of the atmosphere. A tiny wind got started and then it just grew and grew and grew because there was very little turbulence to slow it down. The super fast winds had polished the surface smooth over the past few millions of years. So I suppose the cyclical cooling and heating of the earth creates turbulence in the atmosphere that helps prevent the setting up of any net movement of the atmosphere relative to the earth?? The turbulence helps the atmosphere "stick" to the earth!?! Maybe you're right up to a point? Maybe it's the extra turbulence that causes the earth's atmosphere to move, in general, in step with the rotation of the earth? If the experts can get their predictions wrong then maybe it is quite complicated after all!

Question:1. Does the Axis of earth makes a fixed angel with the Orbit (around the Sun) or the angel changes with the postion on the Eliptical Orbit.I mean , whether the axis postion is parellel thru out the orbit or not ? 2. Is Equator parallel to the Orbit of the earth or it makes equal angel as the Axis makes with the Orbital path ? 3.Is the Orbit around Sun perfectly Eliptical and symetric ? 4.If yes, why dont' we experiance 2 Summers and 2 winters ? 5.Is the distance of earth from Sun is same On every Equinox ? 6.There are number of websites offering Animation of Earths Rotation and Revolution explaining the Day and Night at the Poles. In your opinion, Which web site shows most easy to understand Animation amongst these ?

Answers:1. The direction of the earth's axis is *relatively* constant throughout the year. But it does (very slowly) rotate, taking about 27000 years to make a complete rotation. This motion is called "precession of the equinoxes. 2. The equator is tilted from the plane of the ecliptic by about 23.4 , which is called the "obliquity" of the axis. The obliquity also changes slowly with time, and is currently decreasing a bit. 2000 years ago, it was about 23.7 . 3. The orbit of earth around the Sun is an ellipse, but it is not a perfect ellipse, due to small perterbations of the Moon and other planets. 4. The ellipticity of Earth's orbit also changes, and at the current time it is fairly low -- meaning that the orbit is almost (but not quite) circular. For that reason, the ellipticity of the orbit plays only a minor role in the seasons: making winter shorter in the northern hemisphere, and longer in the southern hemisphere. 5. The distance between Earth and the Sun is nearly the same from one equinox to the next, but not quite. The position of perihelion (closest point to the sun) also slowly changes over time. Currently perihelion occurs in the first week in January. But 2000 years ago, it was in late autumn. 6. I'll take a pass on that one :-)

Question:if acceleration due to gravity on earth were to increase suddently, would this affect atmospheric pressure?

Answers:respecting the laws of newton it would. taking into account that air has very little mass though... the change i think will me minimal the earth however is at a stable speed. so either way it doesnt realy matter.

3DSMax - 3D Rotating Earth :My first take on rendering the Earth. Atmosphere, ocean reflections, matte landmasses, nightside lights, starmap.

Earth rotation time lapse from Galileo :Galileo Earth spin movie, a 256-frame time-lapse motion picture that shows a 25-hour period of Earth's rotation and atmospheric dynamics.