# Homework Help: Moon physics problem

1. Jun 29, 2010

### JJ89

Suppose that Nolan Ryan stands on the surface of the moon and throws a baseball horizontally. If the baseball has a high enough speed and does not strike any mountain, it can orbit around the moon and, after completing the orbit, strike Nolan from behind. The mass of the moon is mm = 7.35×(10*22power kg), and its radius is rm = 1740 km. The gravitation constant G = 6.67×10(-11power) Nm2/kg2.

a) Find the speed at which Nolan must throw the ball for such a circular orbit? V= ms

(b) How long (in hours) does the ball take to complete one orbit? T= hrs

is the equation V=G*R? if so i used 7.35*10to the 22nd power * 6.67 *10 to -11 power?
i got 4.90245e12, and it said i was wrong.

3. The attempt at a solution

2. Jun 29, 2010

### JJ89

Re: Moon

but i cant figure out the equation for B

3. Jun 29, 2010

### JJ89

Re: Moon

did i do A right?

4. Jun 29, 2010

### kuruman

Re: Moon

No, the equation is not V = G*R. Look up the correct equation for satellite motion in a circular orbit in your textbook. You can also derive it using Newton's Second Law combined with Newton's Law of gravitation.