objects at rest on the Earth's surface move in circular paths with a period of 24hr. why are they not considered to be "in orbit" ? what would be the length of the day to put such objects in true orbits?
2006-09-23 05:03:52 · 5 answers · asked by Anonymous in Science & Mathematics ➔ Physics
Items resting on the ground are not in orbit as you say. An object in orbit circles the earth at a rate that prevents it falling to Earth. If you hold an object in your hand a let it fall, it falls straight down with no lateral motion. If you throw the object parallel to the Earth's surface, it will eventually fall to Earth but not after covering a certain amount of lateral distance. A bullet fired from a gun will cover even more distance before hitting the Earth. So, the faster an object travels the farther is will travel laterally before falling to Earth.
If the Earth was flat and infinite in all directions, an object would eventually have to hit the earth unless it was travelling infinitely fast. But the Earth is curved, so an object travelling quickly enough would fall at a rate equal to the rate the Earth curves away from the object's initial path (which was parallel to the Earth's surface at it's outset) . Therefore, the Earth's gravity attracts the object and the object is actually "falling" to earth continuously.
As the circumference of the Earth is a touch under 25,000 miles, the velocity of an object would determine how long it takes to circumnavigate the Earth. Because an object's orbital velocity varies according to it's altitude above the Earth, a higher orbital height would make for a longer period of circumnavigation. Wikipedia lists the altitude for a geosynchronous orbit (one in which the orbiting object stays over a point on the earth) as about 22,300mi.
2006-09-23 05:22:29 · answer #1 · answered by Adashi 3 · 0⤊ 0⤋
they are not considered in orbit because at the speed they are travelling, they would not be orbiting without the support of the earth. In order to orbit where they are they would have to be moving much faster
2006-09-23 12:11:18 · answer #2 · answered by Greg G 5 · 1⤊ 0⤋
Because they are on the surface. A perfect geostaionary orbit is 24 hours at about 23,000 miles.
2006-09-23 12:12:06 · answer #3 · answered by F T 5 · 0⤊ 1⤋
They are orbiting the sun.
2006-09-23 12:21:56 · answer #4 · answered by Dr M 5 · 0⤊ 0⤋
About 90 mins.
2006-09-23 12:06:19 · answer #5 · answered by christopher N 4 · 0⤊ 1⤋