# Satellite orbit

1. Nov 14, 2006

### john fairbanks

when a satalite orbits the earth my text states that it is constantly falling into the earth as it moves tangentially -- my question is why doesn't the speed of the object falling into the earth increase radially since it is acted upon by the force of gravity, a force of gravity would cause an object to accelerate! so the falling velocity should not be constant like the tangential speed -- in fact all planets should fall into what they are orbiting around. But they don't so please help!

2. Nov 14, 2006

### Danger

Keep in mind that 'acceleration' can mean a change of direction just as properly as a change of speed. A satellite is constantly changing direction as it follows the curvature around its parent.

3. Nov 14, 2006

### ChemGuy

The planets would fall into the sun if they had no "forward" momentum. Think of what would happen if the sun suddenly disappered. The earth would just go in a straight line tanget to the previous orbit. A planet orbits because it has enough forward momentum to exacly balance the pull of gravity.

4. Nov 14, 2006

### ChemGuy

The planets would fall into the sun if they had no "forward" momentum. Think of what would happen if the sun suddenly disappered. The earth would just go in a straight line tanget to the previous orbit. A planet orbits because it has enough forward momentum to exacly balance the pull of gravity.

5. Nov 14, 2006

### john fairbanks

Thnaks for responding, they move tangent to the orbit at a uniform velocity but the force of gravity should accelerate the satellite or planet, just like in our atmosphere, speed increases as a body falls due to gravity. it accelerates, the fall is not a constant speed -- so why does the velocity of the fall of a satellite stay the same. du to accelerationdarisI kno

6. Nov 14, 2006

### john fairbanks

7. Nov 14, 2006

### Danger

The velocity does not remain the same. Velocity is a vector (it entails both speed and direction). Since the direction is constantly changing, so is the velocity... which is the definition of 'acceleration'.