# Orbital speed of mars help?

1. Mar 3, 2008

### rsyodoom2005

orbital speed of mars!! help!?

Mars is 230 million km from the sun. It completes one orbit in a period of approximately 687 days. Calculate the orbital speed of Mars in mph.

OK so gave me the formula which 2*pi*r/ Period r= distance from the planet to the sun. and cirmumference = 2*pi* r

So i set it up 2*3.1416* 150E6 km /16488 hours (mars hours)

= 57161.57 km/hr then convert to mph 57161.57km hour/1.60km =35725.98 mph

2. Mar 3, 2008

### kamerling

I really don't get what you mean by this. what is equal to what? Nor do I understand
any of the rest of the calculations.

You could use that the centripetal acceleration of a planet is proportional to v^2/r
and the acceleration due to gravity is proportional to 1/r^2 and equal to the centripetal
acceleration.

since for the earth c_1 * v^2/r = c_2 /r^2 this must also be valid for mars with the same constants.

3. Mar 3, 2008

### rsyodoom2005

In order to send a spacecraft to the planet Mars you will need to complete some basic orbital equations using Kepler's law of orbits. In the next few Mars Math Questions, we will look at ways engineers calculate this by introducing you to some basic equations and formulas.

. Mars is 230 million km from the sun. It completes one orbit in a period of approximately 687 days. Calculate the orbital speed of Mars in mph.

The equation to determine orbital speed is 2*Pi*r/Period. r = Distance from the planet to the sun. Circumference = 2*Pi*r

So i set it up 2*3.1416* 230E6 km /16488 hours (mars hours) = 87647.74 km/hour

now to convert mph i divided by the conversion factor of 1.60 which gave me 54779.83 mph (orbital speed of mars)??

4. Mar 3, 2008

### kamerling

Oh I see, you get both the period and the radius, so you don't need Keplers laws or acceleration and gravity, but you can just use circumference/period to get the orbital speed.

5. Mar 30, 2010

### DocileRaptor

Re: orbital speed of mars!! help!?

rsyodoom2005

I'd advise you to attempt the WAS math problems on your own. This can be considered cheating.

6. Apr 2, 2011

### Nicook5

Re: orbital speed of mars!! help!?

Not only is it cheating, but its a very easy problem. They give you the formulas... all you need to do is plug the numbers in...