why does an artificial satellite does not fall on earth due to force of gravity?

Answer 1

Conservation of energy. Once placed in an orbit and after the rockets have shut off, there's theoretically only one force affecting the satellite - gravity.

If an object started out stationary in space and if the object could fall through the Earth without slowing down, the Earth's gravity would accelerate the object so that it would fall faster and faster towards the Earth. Once the object reached the center of the Earth, it would be going very fast. Because of it's momentum, it would keep on going unless some force acted on it. The only force acting on it is still gravity, so the object would slow down at the same rate that it sped up. It would reach the same distance away on the opposite side of the Earth before it finally stopped again. The force of gravity would still be the only force acting on the object, so it would fall back towards the Earth, through the Earth, to it's starting point, and so on. There can't be any net work done by gravity from a stationary source.

The difference between a satellite orbit and the motion I described is that the satellite has a sideways motion to it instead of sitting there stationary. If the sideways motion (tangential motion) is fast enough, the satellite misses the Earth on the way down as it speeds up all the way down. It curves around the Earth and slows down all the way up, reaching it's original point with the exact same tangential motion it started with. Whatever gets done on the way down gets undone on the way up - there can't be any net change because the gravity is coming from a stationary point.

The exact same principles apply if you hold a ball in the air and let go of it. Because the Earth is spinning, the ball has a tangential motion and it's released into an orbit around the CENTER of the Earth. Unfortunately, the tangential motion isn't fast enough to miss the Earth. In fact, that particular orbit intersects the Earth in less than half a second.

A side note in response to some of the other posts. Not all satellites re-enter the atmosphere. The atmosphere thins gradually and there's still at least some atmospheric gases up to at least 1000 km (around 600 miles) above the Earth's surface. As thin as it may be, it's still enough to slow satellites down, which is why the low orbiting satellites DO eventually re-enter the atmosphere. Satellites more than a 1000 km high (GPS satellites, geosynchronous communications satellites) never re-enter the atmosphere.

Answer 2

Because of the equilibrium created by the centrifugal force given to it when it was put in orbit. If it slows down then gravity starts to pull it down to earth and eventually it will fall and this is how old satellites die. Satellites usually have small rocket engine to control its speed to keep it in orbit if it slows down. once energy is depleted the satellite will gradually leave its orbit.

Answer 3

Satellites, in addition to falling, also move "forward". As a result, they "fall" around the earth (I wish I had a picture to illustrate it.

Imagine throwing a baseball. As it moves away from you, it starts to fall to the ground some distance away from you. Imagine that you could through the ball so fast, that as it fell, it fell over the horizon.

That is the best I can explain it without drawing a picture.

Satellites eventually do slow down and fall, usually (hopefully) burning up in the atmosphere.

Answer 4

the altiude and speed of a satellite are carefully calculated, the amount that the satellite falls in one second due to gravity matches the curvature of the earth's surface; if the speed remains constant the satellite will remain in orbit.

Answer 5

coz the satellite is orbiting the earth with a a certain velocity and the force of attraction provides for centripetal force. thats why it doesn't fall on earth.

Answer 6

The satelite has a motional power if the motion power matches the gravitational power the two system are in equilibrium and follow the law of inertia. Thus the satelite remains in orbital motion.

Answer 7

Gravity keeps it in orbit as long as it maintains the speed necessary to stay in that orbit - it's stable. Look up orbital velocity.

Answer 8

Well they are actualy falling but they are moving forward so really they are just falling around the Earth.

Answer 9

Because of inertia, which counteracts the gravity and allows the satelitte to stay in orbit.

Answer 10

bcoz of centrifugul force , away from earth which equals gravity.
and sat. are placed too far from earth is aother reason