# Homework Help: How to find the acceleration of a random planet

1. Oct 8, 2004

### justinbaker

here is the question,

the mysterious planet pyramid travels around its sun in a circular orbit. The radius of this planet is 2.69e^7 m and the mass is 3.06e^25 kg . The radius of orbit of pyramid is 1.15e^11 m and the period is 6.34e^7 s . The mass of pyramids sun is 9.22e^31 and the radius of the sun is 1.50e^9 m . What is the acceleration of gravity on pyramid? (m/s^2)

i thought you could use the formula v=(2(pi)r)/T and plug this into F=m(v^2/r) since the only force is gravity towards the sun.

But my answer comes out to be 3.45e^22

this seems a little high, any help? thanks guys

2. Oct 8, 2004

### Staff: Mentor

You have the mass and the radius of the planet. Use Newton's law of gravity to find the acceleration due to gravity at the planet's surface.

3. Oct 8, 2004

### justinbaker

dont i need to use the period somewhere in this problem?

Last edited: Oct 8, 2004
4. Oct 8, 2004

### Staff: Mentor

Not if the problem is to find the acceleration due to gravity on that planet's surface. (Is that the problem?)