1. Oct 31, 2007

### JohnJay

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

What is the ratio of the earth's orbital period about the sun to the earth's period of rotation about its own axis

2. Relevant equations

none, theory

3. The attempt at a solution

Its theory

Two 335 kg masses (744 lb) are separated by a distance of 5 m. Using Newton's law of gravitation, find the magnitude of the gravitational force exerted by one mass on the other.

F = Gm1m2
______
r (squared)

God... I'm putting it in, but it says its wrong... help....

Joe has a weight of 750 N (about 170 lb) when he is standing on the surface of the earth. What would his weight (the gravitational force due to the earth) be if he tripled his distance from the center of the earth by flying in a spacecraft?

The formula should be...

w x a = f

Thank you members of the community

Last edited: Oct 31, 2007
2. Oct 31, 2007

### Kurdt

Staff Emeritus
The first question should be fairly easy. I assume you've been given the information about both periods of rotation.

For the two masses what answer are you getting? That might help in diagnosing whats going wrong.

Weight is defined as W=mg, where:

$$g= G\frac{M_E}{r^2}$$

What will his weight be if r is tripled?

3. Nov 1, 2007

### Staff: Mentor

What is the definition of a year timewise? What is significant about the length of a day?

For the second problem, please show the values used, e.g. gravitational constant, G, in the formula.

4. Nov 1, 2007

### JohnJay

Umm it doesnt say...

and grav. should be 9.81

5. Nov 1, 2007

### Kurdt

Staff Emeritus
What do you think are the periods for the period of rotation of the Earth and the period of the Earth round the sun. Its fairly obvious.

No, g = 9.81 ms-2 and G = 6.67x10-11 m3kg-1 s-2