# Strange question

#### walker

So I came across a question in a quiz book the other day and I still haven't been able to answer it, so I figured I would ask some experts... Here goes...

As a NASA senior physicist, would you agree with the calculation made by a junior physicist regarding the speed of an artificial satellite, v = 3 x 10^4 m/s, assuming that it is travelling at an altitude h = 230 km above the earth's surface where g = 9.0 m/s^2. The radius of the earth is 6370 km.

Related Other Physics Topics News on Phys.org

#### chroot

Staff Emeritus
Gold Member
I would disagree.

For all circular motion, a = v2/r, where a is the centripetal acceleration, v is the linear velocity, and r is the radius of the circle.

Plug the numbers in, and you'll see there's a contradiction.

The satellite should be moving at roughly 7,000 m/s, not 30,000 m/s.

- Warren

#### enigma

Staff Emeritus
Gold Member
Yep,

If the sat is going at that speed and altitude, it won't be at that altitude for long.

### Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving