# Satellite physics problem

1. Nov 6, 2013

### Coco12

1. The problem statement, all variables and given/known data

a satellite will remain in orbit such that the centripetal acceleration is equal to the acceleration due to gravity. The radius of the satellites orbit is 6.37*10^6m. What speed must the satellite travel to stay in orbit?

2. Relevant equations

ac=v^2/r

3. The attempt at a solution

Would I just take the sqrt of ac*r to get the velocity?

2. Nov 6, 2013

### nasu

This is a good start. But do you know ac?

3. Nov 6, 2013

### Coco12

Won't ac be 9.8? Since it is equal to acc due to gravity?

4. Nov 6, 2013

### UltrafastPED

That's only valid at the surface of the earth ... do you know how to find it at any distance from the center of the earth? That is what you need!

5. Nov 6, 2013

### Coco12

How do u find it?

6. Nov 6, 2013

### UltrafastPED

Newton's Universal Law of Gravitation ... F = G mM/r^2.

7. Nov 7, 2013

### Coco12

mM stands for?

8. Nov 7, 2013

### UltrafastPED

Mass of earth, mass of satellite.

9. Nov 7, 2013

### Staff: Mentor

Compare that to the radius of the Earth. Seems that the satellite is just skimming the surface. Is that the intention?

10. Nov 7, 2013

### Coco12

I think so because we did not learn the formula: newtons gravitational force yet. We only learned about ac and FC and simple harmonic motion. So I don't think the teacher will give us something that we never used yet??

11. Nov 7, 2013

### UltrafastPED

In that case use acceleration = 9.8 m/s/s